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HVAC System - Manual - Old Style Cadillac Escalade GMT400

Manual HVAC System 18 illustrations ~9325 words

SPECIFICATIONS

Note. In addition to Escalade, Tahoe and Yukon, this article applies to Pickup Classic, for Sierra and Silverado see appropriate article.

ApplicationSpecification
Compressor TypeDelphi Thermal HT6 6-Cyl. Axial
Compressor Belt Tension(1)
Refrigerant (R-134a) Capacity
"C & "K" Pickup (Classic) & Sierra32 ozs.
Crew Cab & Utility36 ozs.
Suburban
With Rear Unit56 ozs.
Without Rear Unit32 ozs.
Escalade, Tahoe & Yukon
With Rear Unit44 ozs.
Without Rear Unit32 ozs.
System Oil Capacity (2)
Pickup (Classic) & Sierra8 ozs.
Crew Cab & Utility8 ozs.
Escalade, Suburban, Tahoe & Yukon
With Rear Unit11 ozs.
Without Rear Unit8 ozs.
System Operating Pressures (3)
High Side228 psi (16.0 kg/cm 2 )
Low Side34 psi (2.4 kg/cm 2 )
(1) Belt tension is adjusted automatically by a spring-tensioned idler pulley. Belt adjustment is not required. (2) Use PAG refrigerant oil. (3) Specification is with ambient temperature at 70°F (21°C), relative humidity of 70 percent and engine speed at 2000 RPM.
(1)Belt tension is adjusted automatically by a spring-tensioned idler pulley. Belt adjustment is not required.
(2)Use PAG refrigerant oil.
(3)Specification is with ambient temperature at 70°F (21°C), relative humidity of 70 percent and engine speed at 2000 RPM.

SPECIFICATIONS

DESCRIPTION

Note. This article applies to Pickup Classic, for Sierra and Silverado see appropriate article.

WARNINGTo avoid injury from accidental air bag deployment, read and carefully follow all SERVICE PRECAUTIONS and DISABLING & ACTIVATING AIR BAG SYSTEM procedures in AIR BAG SYSTEM SAFETY article in GENERAL SERVICING.

The A/C system is a Cycling Clutch Orifice Tube (CCOT) type, with a fixed displacement compressor, and a pressure cycling switch to control evaporator temperature. Electric motors are used to control mode, temperature, and recirculation doors. A series of relays and a resistor are used to control blower motor speed. Motors and relays are controlled by A/C-heater control assembly knobs. The A/C-heater system is a blend-air system. Air entering vehicle passes through evaporator core and through, or around, heater core to provide desired temperature.

Suburban, may be equipped with an optional auxiliary (rear unit) A/C or A/C-heater system. Auxiliary system operates with main A/C-heater system, but has separate blower controls.

Temperature Control Knob

Temperature control knob (left knob) is located below radio. Temperature door is controlled by an electric actuator, based on temperature knob position. When temperature knob is in cold (Blue) position, air delivered by system is unheated. When temperature knob is in hot (Red) position, all air passing through heater module is heated before it is discharged. Intermediate position of temperature knob results in a mixture of heated and unheated air to provide moderate air temperatures.

Blower Switch

Blower switch (center knob) provides various blower speeds. Blower switch receives power through a fuse in fuse block when ignition is on. There are 4-fan speeds: LO, HI and 2 intermediate positions, and an OFF position. Blower operates in any position except OFF. (Scheme 1)

Mode Selector Knob

Mode selector knob controls various actuators on A/C-heater system. Each actuator operates a door that routes airflow to various outlets through the system. Mode selector knob (right knob) positions are vent, vent/heat, heat, heat/defrost, and defrost. (Scheme 1)

Recirculation Button

Button is located between temperature control knob and blower switch. When pressed, air is allowed to recirculate inside vehicle. This helps maximize A/C performance and fuel economy. This setting cools air faster and prevents dust from entering vehicle.

A/C Button

Button is located between blower switch and mode selector knob. Button activates A/C system. Air coming into vehicle is cooled and directed through instrument panel vents. (Scheme 1)

Scheme 1

Scheme 1: A/C Button
Scheme 1: A/C Button

Front Auxiliary HVAC Control Assembly

Front auxiliary Heating, Ventilation, and Air Conditioning (HVAC) control assembly is located in center of headliner, above rear view mirror. (Scheme 2) Features of the front auxiliary HVAC control assembly are control of auxiliary blower motor at one of 3-speeds, OFF, REAR CNTL, upper vent, lower vent and temperature. When any position other than REAR CNTL is selected, control of rear auxiliary HVAC assembly is from front auxiliary HVAC control assembly. When main system is off or not in A/C mode, auxiliary blower switch can operate blower motor to circulate air in rear passenger compartment.

Scheme 2

Scheme 2: Front Auxiliary HVAC Control Assembly
Scheme 2: Front Auxiliary HVAC Control Assembly

Rear Auxiliary HVAC Control Assembly

Rear auxiliary HVAC control assembly is located overhead, behind front seats. When front auxiliary HVAC control assembly is set to REAR CNTL on Suburban, rear auxiliary HVAC control assembly regulates temperature, auxiliary blower motor speeds, and mode operation, with the exception of REAR CNTL mode. (Scheme 3) When front auxiliary HVAC control is set to REAR CNTL on Tahoe and Yukon, rear auxiliary HVAC control assembly regulates auxiliary blower motor speeds only.

Scheme 3

Scheme 3: Rear Auxiliary HVAC Control Assembly
Scheme 3: Rear Auxiliary HVAC Control Assembly

HIGH PRESSURE CUT-OFF SWITCH

The high pressure cut-off switch, located on rear of compressor, is designed to interrupt compressor operation in the event of excessively high operating pressure. Switch is normally closed and will open if pressure exceeds 410-450 psi (28.8-31.6 kg/cm 2 ).

PRESSURE CYCLING SWITCH

Note. Pressure cycling switch may also be referred as low pressure cut-off switch.

Switch is mounted on a Schrader valve type fitting and controls compressor operation. If low-side pressure decreases to approximately 23 psi (1.6 kg/cm 2 ), switch opens, interrupting power to A/C compressor clutch. When pressure increases to about 46 psi (3.2 kg/cm 2 ), switch closes, providing power to clutch. Switch maintains evaporator surface at a temperature slightly warmer than freezing (45 degrees F), to prevent evaporator icing and airflow blockage during normal system operation.

HIGH PRESSURE RELIEF VALVE

High pressure relief valve, located near compressor, protects refrigerant system from excessively high pressure. If high-side pressure exceeds 410-460 psi (28-31 kg/cm 2 ), valve opens, venting refrigerant to prevent system damage.

ACTUATORS

Before installing actuator, connect electrical connector. Turn ignition switch to ON position. Allow actuator to position itself. Turn ignition switch to OFF position and disconnect actuator electrical connector. Install actuator. (Scheme 4)

Scheme 4

Scheme 4: ACTUATORS
Scheme 4: ACTUATORS

TROUBLE SHOOTING

WARNINGTo avoid injury from accidental air bag deployment, read and carefully follow all SERVICE PRECAUTIONS and DISABLING & ACTIVATING AIR BAG SYSTEM procedures in AIR BAG SYSTEM SAFETY article in GENERAL SERVICING.

Note. For additional trouble shooting information, see MANUAL A/C-HEATER SYSTEMS - TROUBLE SHOOTING article.

FUNCTIONAL CHECK

  1. The operation of the air conditioning blower at all speeds, in any position except the OFF position, and the engagement of the compressor clutch indicate that the electrical circuits are functioning properly.
  2. The same hand-felt temperature of the evaporator inlet pipe and the accumulator surface of an operating system indicates a properly charged system.
  3. The operation of the air conditioning control head in the distribution of air from the designated outlets indicates proper functioning.

AIR DELIVERY SYSTEM CHECK

Note. If vehicle is equipped with auxiliary A/C system, perform all test steps. If vehicle is equipped with front A/C only, perform steps 1) to 3).

  1. Start engine and bring to operating temperature. Turn blower switch to high position. Rotate temperature knob to full hot (Red) position. Rotate mode control knob through each position. Air temperature should be hot and blower motor should operate at high speed. With mode control in defrost position, air will exit from defrost outlets. In bi-level or blend position, air will exit from defrost and heater (floor) outlets. In heater position, air will exit from heater (floor) outlets. In vent position, air will exit from instrument panel vent (A/C) outlets. If airflow does not change as specified, go to «FRONT MODE DOOR ACTUATOR INOPERATIVE»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__front-mode-door-actuator-inoperative) .
  2. Rotate temperature knob to full cold (Blue) position. Rotate mode control knob through each position. Air temperature will change from hot to cool. If air temperature does not change as specified, go to «FRONT TEMPERATURE ACTUATOR INOPERATIVE»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__front-temperature-actuator-inoperative) .
  3. Depress A/C button, to turn A/C on, and rotate temperature knob to maximum cold (Blue) position. Depress A/C button, to turn A/C off, and rotate temperature knob to medium (Red/Blue) position. Depress recirculation button to recirculate air within passenger compartment. Airflow changing between fresh and recirculated air will be heard as a loud rushing sound and increase in blower motor output velocity. If no change can be detected, go to «FRONT AIR INLET ACTUATOR INOPERATIVE»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-inlet-actuator-inoperative) .
  4. Place front auxiliary A/C-heater control assembly blower switch in high position. Front auxiliary A/C-heater control assembly is located overhead, above rear view mirror. Turn mode control knob to lower outlet position and turn temperature control to full cold (Blue) position. Auxiliary blower motor should operate at high speed and cold air should flow from lower outlets of the auxiliary A/C system. If air is not cold, go to «AUXILIARY TEMPERATURE ACTUATOR INOPERATIVE»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__auxiliary-temperature-actuator-inoperative) . If air does not flow from lower outlets, go to «AUXILIARY MODE ACTUATOR INOPERATIVE»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__auxiliary-mode-door-actuator-inoperative) .
  5. Place front auxiliary A/C-heater control assembly mode control knob to upper outlet position and turn temperature control to full hot (Red) position. Auxiliary blower motor should operate at high speed and hot air should flow from upper outlets of auxiliary A/C system. If air is not hot, go to «AUXILIARY TEMPERATURE ACTUATOR INOPERATIVE»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__auxiliary-temperature-actuator-inoperative) . If air does not flow from upper outlets, go to «AUXILIARY MODE ACTUATOR INOPERATIVE»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__auxiliary-mode-door-actuator-inoperative) .
  6. Place front auxiliary A/C-heater control assembly in REAR position. Go to rear auxiliary A/C-heater control assembly, located above rear headliner. Turn blower switch to high position, mode control knob to lower outlet position and temperature control to full cold (Blue) position. Auxiliary blower motor should operate at high speed and cold air should flow from lower outlets of auxiliary A/C system. If air is not cold, go to «AUXILIARY TEMPERATURE ACTUATOR INOPERATIVE»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__auxiliary-temperature-actuator-inoperative) . If air does not flow from lower outlets, go to «AUXILIARY MODE ACTUATOR INOPERATIVE»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__auxiliary-mode-door-actuator-inoperative) .
  7. Place rear auxiliary A/C-heater control assembly mode control knob to upper outlet position and turn temperature control to full hot (Red) position. Auxiliary blower motor should operate at high speed and hot air should flow from upper outlets of auxiliary A/C system. If air is not hot, go to «AUXILIARY TEMPERATURE ACTUATOR INOPERATIVE»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__auxiliary-temperature-actuator-inoperative) . If air does not flow from upper outlets, go to «AUXILIARY MODE ACTUATOR INOPERATIVE»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__auxiliary-mode-door-actuator-inoperative) .

A/C COMPRESSOR CLUTCH INOPERATIVE

  1. Perform appropriate REFRIGERANT SYSTEM DIAGNOSIS procedure in MANUAL A/C-HEATER SYSTEMS - TROUBLE SHOOTING article. Go to next step.
  2. Disconnect A/C compressor clutch connector. Start engine and allow it to idle. Adjust mode control knob to floor position. Adjust temperature control to maximum cooling. Turn front blower switch to HI position. Depress A/C button on front A/C-heater control assembly. Verify that LED illuminates on A/C button. Use a DVOM to check for continuity between A/C compressor clutch connector terminal "A" (Black wire) and ground. See «WIRING DIAGRAMS»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style) . If continuity is indicated, go to next step. If continuity is not indicated, go to step 25 .
  3. Remove A/C compressor clutch relay from underhood fuse block. Use a DVOM to check for continuity between A/C compressor clutch relay cavity terminal A6 and compressor clutch connector terminal"B" (Dark Green wire). If continuity is indicated, go to next step. If continuity is not indicated, go to step 26 .
  4. Turn ignition switch to ON position. Connect a test light between A/C compressor clutch relay cavity terminal B4 (Orange wire) and ground. If test light comes on, go to next step. If test light does not come on, go to step 27 .
  5. Connect a test light between A/C compressor clutch relay cavity terminal A4 (Pink wire) and ground. If test light comes on, go to next step. If test light does not come on, go to step 28 .
  6. On diesel models, disconnect PCM 32-pin Blue connector C3. Use a DVOM to check for continuity between A/C compressor clutch relay cavity terminal B6 and PCM connector C3, terminal D5 (Dark Green/White wire). On gasoline models, disconnect VCM 32-pin Gray connector C3. Use a DVOM to check for continuity between A/C compressor clutch relay cavity terminal B6 and VCM connector C3 terminal No. 1 (Dark Green/White wire). If continuity is indicated, go to next step. If continuity is not indicated, go to step 29 .
  7. Reinstall A/C compressor clutch relay. On diesel models, connect a fused jumper between PCM connector C3, terminal D5 (Dark Green/White wire) and ground. On gasoline models, connect a fused jumper between VCM connector C3 terminal No. 1 (Dark Green/White wire) and ground. Connect a test light between A/C compressor clutch connector terminal "B" (Dark Green wire) and ground. If test light comes on, go to next step. If test light does not come on, go to step 30 .
  8. If vehicle is equipped with a gasoline engine, go to next step. If vehicle is equipped with a diesel engine, go to step 11 .
  9. Use a DVOM to check for continuity between VCM 32-pin connector C3 terminal No. 17 (Black/White wire) and ground. If continuity is indicated, go to next step. If continuity is not indicated, go to step 31 .
  10. Use a DVOM to check for continuity between VCM 32-pin connector C3 terminal No. 18 (Black/White wire) and ground. If continuity is indicated, go to step 13 . If continuity is not indicated, go to step 32 .
  11. Use a DVOM to check for continuity between PCM 32-pin connector C3, terminal D7 (Tan/White wire) and ground. If continuity is indicated, go to next step. If continuity is not indicated, go to step 33 .
  12. Use a DVOM to check for continuity between PCM 32-pin connector C3 terminal D6 (Black/White wire) and ground. If continuity is indicated, go to step 14 . If continuity is not indicated, go to step 34 .
  13. Use a DVOM to check for continuity between VCM 32-pin connector C3 terminal No. 25 (Dark Green/White wire) and ground. If continuity is indicated, go to step 15 . If continuity is not indicated, go to step 35 .
  14. Disconnect PCM 32-pin Brown connector C1. Connect a test light between PCM connector C3, terminal C2 (Dark Green/White wire) and ground. If test light comes on, go to next step. If test light does not come on, go to step 36 .
  15. Disconnect A/C high pressure switch. Switch is located on rear of compressor. On diesel models, use a DVOM to check for continuity between PCM connector C1, terminal C2 and A/C high pressure switch connector terminal "A" (Dark Green/White wire). On gasoline models, use a DVOM to check for continuity between VCM connector C3 terminal No. 25 and A/C high pressure switch connector terminal "A" (Dark Green/White wire). If continuity is indicated, go to next step. If continuity is not indicated, go to step 37 .
  16. Use a DVOM to check for continuity between A/C high pressure switch connector terminals. If continuity is indicated, go to next step. If continuity is not indicated, go to step 38 .
  17. If vehicle is equipped with a gasoline engine, go to next step. If vehicle is equipped with a diesel engine, go to step 19 .
  18. Disconnect A/C compressor cycling switch. Use DVOM to check for continuity between A/C high pressure switch connector terminal "B" and A/C compressor cycling switch connector terminal "B" (Dark Green wire). If continuity is indicated, go to step 20 . If continuity is not indicated, go to step 39 .
  19. With A/C high pressure switch disconnected, disconnect A/C-heater control assembly 10-pin Gray connector C3. Use a DVOM to check for continuity between A/C high pressure switch connector terminal "B" and A/C-heater control assembly connector C3 terminal No. 10 (Light Green wire). If continuity is indicated, go to next step. If continuity is not indicated, go to step 40 .
  20. Reconnect all VCM or PCM connectors. Reconnect A/C compressor clutch connector. Connect a fused jumper between A/C compressor cycling switch connector terminal "B" (Dark Green wire) and battery voltage. Use a DVOM to check for continuity between A/C compressor cycling switch connector terminals "A" (Light Green wire) and "B" (Dark Green wire). Compressor should cycle off and on. If continuity is indicated, go to next step. If continuity is not indicated, go to step 41 .
  21. If vehicle is equipped with a gasoline engine, go to next step. If vehicle is equipped with a diesel engine, go to step 42 .
  22. Remove fused jumper wire between A/C compressor cycling switch and battery voltage. Disconnect A/C-heater control assembly 10-pin Gray connector C3. Use a DVOM to check for continuity between connector C3 and A/C compressor cycling switch connector terminal "A" (Light Green wire). If continuity is indicated, go to next step. If continuity is not indicated, go to step 42 .
  23. Reconnect A/C compressor cycling switch. Connect a test light between A/C-heater control assembly connector C3 terminal No. 5 (Brown wire) and ground. If test light comes on, go to next step. If test light does not come on, go to step 43 .
  24. Use a DVOM to check continuity between A/C-heater control assembly connector C3 terminal No. 5 (Brown wire) and ground. If continuity is indicated, go to step 44 . If continuity is not indicated, go to step 45 .
  25. Repair open in Black wire between A/C compressor clutch and ground. Recheck system operation.
  26. Repair open in Dark Green wire between underhood fuse block and A/C compressor clutch. Recheck system operation.
  27. Repair open in Orange wire between A/C fuse (10-amp) in underhood fuse block and A/C compressor clutch relay. Recheck system operation.
  28. Repair open in Pink wire between A/C compressor clutch relay and IGN E fuse (10-amp) in underhood fuse block. Recheck system operation.
  29. Repair open in Dark Green wire between A/C compressor clutch relay and PCM/VCM. Recheck system operation.
  30. Replace A/C compressor clutch relay. Recheck system operation.
  31. Repair open in Black/White wire between VCM connector C3 terminal No. 17 and ground. Recheck system operation.
  32. Repair open in Black/White wire between VCM connector C3 terminal No. 18 and ground. Recheck system operation.
  33. Repair open in Tan/White wire between PCM connector C3, terminal D7 and ground. Recheck system operation.
  34. Repair open in Black/White wire between PCM connector C3, terminal D6 and ground. Recheck system operation.
  35. Replace VCM. Recheck system operation.
  36. Replace PCM. Recheck system operation.
  37. Repair open in Dark Green wire between A/C high pressure switch and PCM/VCM. Recheck system operation.
  38. Replace A/C high pressure switch. Recheck system operation.
  39. Repair open in Dark Green wire between A/C compressor cycling switch and A/C high pressure switch. Recheck system operation.
  40. Repair open in Light Green wire between A/C high pressure switch and A/C-heater control assembly connector C3. Recheck system operation.
  41. Replace A/C high pressure switch. Recheck system operation.
  42. Repair open in Light Green wire between A/C-heater control assembly connector C3 and A/C compressor cycling switch. Recheck system operation.
  43. Repair open in Brown wire between instrument panel fuse block and A/C-heater control assembly connector C3. Recheck system operation.
  44. Replace A/C-heater control assembly. See «A/C-HEATER CONTROL ASSEMBLY»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style) under REMOVAL & INSTALLATION. Recheck system operation.
  45. Repair open in Black wire between A/C compressor clutch and ground. Recheck system operation.

BLOWER CONTROLS SYSTEM CHECK

See TROUBLE SHOOTING in HEATER SYSTEMS - RWD TRUCKS & VANS - EXCEPT TRACKER article.

BLOWER MOTOR INOPERATIVE

See TROUBLE SHOOTING in HEATER SYSTEMS - RWD TRUCKS & VANS - EXCEPT TRACKER article.

BLOWER MOTOR INOPERATIVE AT HIGH SPEED

See TROUBLE SHOOTING in HEATER SYSTEMS - RWD TRUCKS & VANS - EXCEPT TRACKER article.

BLOWER MOTOR OPERATES AT HIGH SPEED ONLY

See TROUBLE SHOOTING in HEATER SYSTEMS - RWD TRUCKS & VANS - EXCEPT TRACKER article.

BLOWER MOTOR INOPERATIVE AT MEDIUM-HIGH (M2) POSITION

See TROUBLE SHOOTING in HEATER SYSTEMS - RWD TRUCKS & VANS - EXCEPT TRACKER article.

BLOWER MOTOR INOPERATIVE AT MEDIUM-LOW (M1) POSITION

See TROUBLE SHOOTING in HEATER SYSTEMS - RWD TRUCKS & VANS - EXCEPT TRACKER article.

BLOWER MOTOR INOPERATIVE AT LOW SPEED

See TROUBLE SHOOTING in HEATER SYSTEMS - RWD TRUCKS & VANS - EXCEPT TRACKER article.

BLOWER MOTOR OPERATES CONTINUOUSLY

See TROUBLE SHOOTING in HEATER SYSTEMS - RWD TRUCKS & VANS - EXCEPT TRACKER article.

AUXILIARY BLOWER MOTOR INOPERATIVE

  1. Perform «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) . Go to next step.
  2. Disconnect front auxiliary A/C-heater control assembly. Use a DVOM to check for continuity between auxiliary blower switch connector terminal "B" (Black wire) and ground. See «WIRING DIAGRAMS»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style) . If continuity is indicated, go to step 4 . If continuity is not indicated, go to next step.
  3. Repair open in Black wire between auxiliary blower switch connector terminal "B" and ground. Go to «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) .
  4. Use a DVOM with negative lead connected to terminal "B" of front auxiliary A/C-heater control assembly and check for continuity to remaining terminals on A/C-heater control assembly. Rotate switch through all blower speeds. See «AUXILIARY A/C-HEATER CONTROL ASSEMBLY TEST»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style) table. If continuity is as specified, go to step 6 . If continuity is not as specified, go to next step . AUXILIARY A/C-HEATER CONTROL ASSEMBLY TEST Switch Position Continuity Between Terminals Off (1) (2) None Low (1) B & C; (2) F & C Medium (1) B & E; (2) F & E High (1) B & D; (2) F & D Rear (1) B & F (1) Front auxiliary A/C-heater control assembly. (2) Rear auxiliary A/C-heater control assembly.
  5. Replace front auxiliary A/C-heater control assembly. See «AUXILIARY A/C-HEATER CONTROL ASSEMBLY»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__removal-installation-front-overhead-console) under REMOVAL & INSTALLATION. Go to «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) .
  6. Disconnect auxiliary blower motor resistor (located on top of auxiliary heater unit, near right rear wheelwell). Disconnect auxiliary blower motor connector. Use a DVOM to check for continuity in Yellow wire between auxiliary blower motor resistor connector terminal "B" and auxiliary blower motor connector terminal "A". If continuity is indicated, go to step 8 . If continuity is not indicated, go to next step.
  7. Repair open in Yellow wire between auxiliary blower motor resistor and auxiliary blower motor. Go to «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) .
  8. Use a DVOM to check for continuity between ground and auxiliary blower motor connector terminal "B" (Black wire). If continuity is indicated, go to next step. If continuity is not indicated, go to step 10 .
  9. Replace auxiliary blower motor. See «AUXILIARY BLOWER MOTOR & FAN»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style) under REMOVAL & INSTALLATION. Go to «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) .
  10. Repair open in Black wire between auxiliary blower motor and ground. Go to «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) .

AUXILIARY BLOWER MOTOR INOPERATIVE AT HIGH SPEED

  1. Perform «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) . Go to next step.
  2. Remove auxiliary blower motor high speed relay. Relays are located on top of auxiliary heater unit, near right rear wheelwell. Connect a fused jumper between relay cavity terminals No. 1 (Red wire) and 4 (Yellow wire). See «WIRING DIAGRAMS»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style) . If auxiliary blower motor runs, go to next step. If auxiliary blower motor does not run, go to step 4 .
  3. Replace auxiliary blower motor high speed relay. Go to «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) .
  4. Disconnect front auxiliary A/C-heater control assembly. Use a DVOM to check for continuity between terminals "B" and "D" of front auxiliary A/C-heater control assembly. Rotate switch to high position. Use a DVOM to check for continuity between terminals "B" and "F" of front auxiliary A/C-heater control assembly. Rotate switch to rear position. If continuity is indicated in both positions, go to step 6 . If continuity is not indicated, go to next step.
  5. Replace front auxiliary A/C-heater control assembly. See «AUXILIARY A/C-HEATER CONTROL ASSEMBLY»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__removal-installation-front-overhead-console) under REMOVAL & INSTALLATION. Go to «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) .
  6. Disconnect rear auxiliary A/C-heater control assembly. Use a DVOM to check for continuity between terminals "F" and "D" of rear auxiliary A/C-heater control assembly. Rotate switch to high position. If continuity is indicated, go to step 8 . If continuity is not indicated, go to next step.
  7. Replace rear auxiliary A/C-heater control assembly. See «AUXILIARY A/C-HEATER CONTROL ASSEMBLY»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__removal-installation-rear-overhead-console) under REMOVAL & INSTALLATION. Go to «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) .
  8. Disconnect auxiliary blower motor connector. Use a DVOM to check for continuity between auxiliary blower motor high speed relay cavity terminal No. 4 and auxiliary blower motor connector terminal "A" (Yellow wire). If continuity is indicated, go to step 10 . If continuity is not indicated, go to next step .
  9. Repair open in Yellow wire between auxiliary blower motor high speed relay and auxiliary blower motor. Go to «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) .
  10. Use a DVOM to measure voltage between auxiliary blower motor high speed relay cavity terminal No. 1 (Red wire) and ground. If battery voltage is indicated, go to step 12 . If battery voltage is not indicated, go to next step.
  11. Repair open in Red wire between auxiliary blower motor high speed relay and splice S401. Splice S401 is located approximately 5" (13 cm) from auxiliary blower motor connector. Go to «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) .
  12. Repair open in White wire between auxiliary blower motor high speed relay cavity terminal No. 2 and front auxiliary A/C-heater control assembly connector terminal "D". Go to «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) .

AUXILIARY BLOWER MOTOR OPERATES IN HIGH SPEED ONLY

  1. Perform «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) . Go to next step.
  2. Disconnect auxiliary blower motor resistor connector. Connect a fused jumper wire between terminals "A" (Light Blue wire) and "B" (Yellow wire). See «WIRING DIAGRAMS»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style) . Turn front auxiliary A/C-heater control assembly to medium position. If auxiliary blower motor turns on, go to next step. If auxiliary blower motor does not turn on, go to step 4 .
  3. Replace auxiliary blower motor resistor. See «AUXILIARY BLOWER MOTOR & FAN»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style) under REMOVAL & INSTALLATION. Go to «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) .
  4. Disconnect auxiliary blower motor connector. Use a DVOM to check for continuity in Yellow wire between auxiliary blower motor resistor connector terminal "B" and auxiliary blower motor connector terminal "A". If continuity is indicated, go to step 6 . If continuity is not indicated, go to next step.
  5. Repair open in Yellow wire between auxiliary blower motor resistor and splice S402. Splice S402 is located approximately 2.5" (7 cm) from blower motor resistor harness breakout, going toward relays. Go to «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) .
  6. Reconnect all disconnected components. Remove both auxiliary blower motor low and medium speed relays. Connect fused jumper wires between both relay cavity terminals No. 2 and 5. Turn front auxiliary A/C-heater control assembly blower switch to low and medium positions. If blower motor operates in both positions, go to step 10 . If blower motor does not operate in both positions, go to next step.
  7. Disconnect front and rear auxiliary A/C-heater control assemblies. With negative lead of DVOM connected to terminal "B" of front auxiliary A/C-heater control assembly, check for continuity at terminals "C" and "E" with switch in low and medium positions. With negative lead of DVOM connected to terminal "F" of rear auxiliary A/C-heater control assembly, check for continuity at terminals "C" and "E" with switch in low and medium positions. If continuity is indicated in both positions, go to step 9 . If continuity is not indicated in both positions, go to next step.
  8. Replace faulty auxiliary A/C-heater control assembly. See «AUXILIARY A/C-HEATER CONTROL ASSEMBLIES»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style) under REMOVAL & INSTALLATION. Go to «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) .
  9. Repair open in suspect relay circuit between cavity terminal No. 2 and auxiliary A/C-heater control assembly connector. Go to «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) .
  10. Replace auxiliary blower motor low and medium speed relays. Go to «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) .

AUXILIARY BLOWER MOTOR INOPERATIVE AT MEDIUM SPEED

Note. Auxiliary blower motor medium speed relay has two Red wires. Red wire, direct feed from convenience center, is hot at all times. The other Red wire is a switching wire to both auxiliary A/C-heater control assemblies.

  1. Perform «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) . Go to next step.
  2. Remove auxiliary blower motor medium speed relay. Relays are located on top of auxiliary heater unit, near right rear wheelwell. Connect a fused jumper wire between relay cavity terminals No. 1 (Red wire) and 4 (Yellow wire). See «WIRING DIAGRAMS»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style) . If auxiliary blower motor runs, go to next step. If auxiliary blower motor does not run, go to step 4 .
  3. Replace auxiliary blower motor medium speed relay. Go to «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) .
  4. Disconnect front and rear auxiliary A/C-heater control assemblies. Use a DVOM to check for continuity between terminals "B" and "E", and "B" and "F" of front auxiliary A/C-heater control assembly. Use a DVOM to check for continuity between terminals "E" and "F" of rear auxiliary A/C-heater control assembly. Rotate blower switches to medium position. If continuity is indicated for both switches, go to step 6 . If continuity is not indicated at one or both switches, go to next step.
  5. Replace faulty auxiliary A/C-heater control assembly. See «AUXILIARY A/C-HEATER CONTROL ASSEMBLIES»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style) under REMOVAL & INSTALLATION. Go to «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) .
  6. Disconnect auxiliary blower resistor connector. Use a DVOM to check for continuity between terminals "A" (Light Blue wire) and "B" (Yellow wire). If continuity is indicated, go to step 8 . If continuity is not indicated, go to next step.
  7. Replace auxiliary blower motor resistor. See «AUXILIARY BLOWER MOTOR & FAN»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style) under REMOVAL & INSTALLATION. Go to «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) .
  8. Use a DVOM to measure voltage between auxiliary blower motor medium speed relay cavity terminal No. 1 (Red wire) and ground. If battery voltage is indicated, go to step 10 . If battery voltage is not indicated, go to next step.
  9. Repair open in Red wire between auxiliary blower motor medium speed relay and splice S401. Splice S401 is located approximately 5" (13 cm) from auxiliary blower motor connector. Go to «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) .
  10. Repair open in Red wire between auxiliary blower motor medium speed relay cavity terminal No. 2 and terminal "E" of front and rear auxiliary A/C-heater control assembly connectors. Go to «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) .

AUXILIARY BLOWER MOTOR INOPERATIVE AT LOW SPEED

  1. Perform «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) . Go to next step.
  2. Remove auxiliary blower motor low speed relay. Relays are located on top of auxiliary heater unit, near right rear wheelwell. Connect a fused jumper wire between relay cavity terminals No. 1 (Red wire) and 4 (Yellow wire). See «WIRING DIAGRAMS»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style) . If auxiliary blower motor runs, go to next step. If auxiliary blower motor does not run, go to step 4 .
  3. Replace auxiliary blower motor low speed relay. Go to «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) .
  4. Disconnect front and rear auxiliary A/C-heater control assemblies. Use a DVOM to check for continuity between terminals "C" and "E" of front and rear auxiliary A/C-heater control assemblies. Rotate blower switches to low position. If continuity is indicated at both switches, go to step 6 . If continuity is not indicated at both switches, go to next step.
  5. Replace faulty auxiliary A/C-heater control assembly. See «AUXILIARY A/C-HEATER CONTROL ASSEMBLIES»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style) under REMOVAL & INSTALLATION. Go to «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) .
  6. Disconnect auxiliary blower resistor connector. Use a DVOM to check for continuity between auxiliary blower motor resistor terminals "B" and "C" (resistor side). If continuity is indicated, go to step 8 . If continuity is not indicated, go to next step.
  7. Replace auxiliary blower motor resistor. See «AUXILIARY BLOWER MOTOR & FAN»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style) under REMOVAL & INSTALLATION. Go to «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) .
  8. Use a DVOM to measure voltage between auxiliary blower motor low speed relay cavity terminal No. 1 (Red wire) and ground. If battery voltage is indicated, go to step 10 . If battery voltage is not indicated, go to next step.
  9. Repair open in Red wire between auxiliary blower motor low speed relay and splice S401. Splice S401 is located approximately 5" (13 cm) from auxiliary blower motor connector. Go to «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) .
  10. Repair open in Dark Blue wire between auxiliary blower motor low speed relay cavity terminal No. 2 and terminal "C" of front and rear auxiliary A/C-heater control assembly connectors. Go to «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) .

AUXILIARY BLOWER MOTOR OPERATES CONTINUOUSLY

Note. Auxiliary blower motor medium speed relay has two Red wires. Red wire, direct feed from convenience center, is hot at all times. The other Red wire is a switching wire to both auxiliary A/C-heater control assemblies.

  1. Perform «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) . Go to next step.
  2. Remove auxiliary blower relays one at a time. Note when blower motor stops and which relay was removed. If blower motor stops, go to next step. If blower motor does not stop after all relays are removed, go to step 4 .
  3. Replace suspect relay. Go to «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) .
  4. With all relays removed, use a DVOM to measure voltage between ground and auxiliary blower motor high speed relay cavity terminal No. 4 (Yellow wire). See «WIRING DIAGRAMS»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style) . If reading is one volt or less, go to «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) . If reading is greater than one volt, go to next step.
  5. Repair short to battery voltage in Yellow wire between auxiliary blower motor, auxiliary blower motor resistor, and auxiliary blower motor high speed relay. Go to «BLOWER CONTROLS SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__blower-controls-system-check) .

FRONT MODE DOOR ACTUATOR INOPERATIVE

  1. Perform «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check). Go to next step.
  2. Turn ignition switch to ON position. Disconnect front mode door actuator connector. (Scheme 4) Use a DVOM to measure voltage between ground and front mode door actuator connector terminal No. 10 (Brown wire). See «WIRING DIAGRAMS»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style). If battery voltage is indicated, go to step 4. If battery voltage is not indicated, go to next step.
  3. Repair open in Brown wire between front mode door actuator connector and splice S243. Splice S243 is located approximately 1.5" (4 cm) from recirculation door actuator harness breakout, toward blower relay. Go to «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check).
  4. Use a DVOM to measure continuity between ground and front mode door actuator connector terminal No. 7 (Black wire). If continuity is indicated, go to step 6. If continuity is not indicated, go to next step.
  5. Repair open in Black wire between front mode door actuator connector and splice S244. Splice S244 is located approximately 3" (8 cm) from recirculation door actuator harness breakout, toward blower relay. Go to «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check).
  6. Turn ignition switch to ON position. Turn blower switch to low position. Ensure that front blower motor operates. Use a DVOM to measure voltage between ground and front mode door actuator connector terminal No. 8 (White wire). Observe DVOM reading while turning mode control knob through all settings. If voltage reading varies smoothly, go to step 9. If voltage reading is erratic and does not vary smoothly, go to next step.
  7. Disconnect A/C-heater control assembly 10-pin connector C3. Use a DVOM to measure voltage between ground and A/C-heater control assembly 10-pin connector C3 cavity terminal No. 9 (control assembly side). Observe DVOM reading while turning mode control knob through all settings. If voltage reading varies smoothly, go to next step. If voltage reading is erratic and does not vary smoothly, go to step 10.
  8. Repair source of high resistance or short in White wire between A/C-heater control assembly and front mode door actuator. Go to «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check).
  9. Remove front mode door actuator and ensure that door moves freely and does not bind. If door is okay, replace front mode door actuator. See «ACTUATORS»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__removal-installation-mode) under REMOVAL & INSTALLATION. Go to «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check).
  10. Replace A/C-heater control assembly. See «A/C-HEATER CONTROL ASSEMBLY»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style) under REMOVAL & INSTALLATION. Go to «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check).

FRONT TEMPERATURE ACTUATOR INOPERATIVE

  1. Perform «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check). Go to next step.
  2. Turn ignition switch to ON position. Disconnect front temperature door actuator connector. (Scheme 4) Use a DVOM to measure voltage between front temperature door actuator connector terminal No. 10 (Brown wire) and ground. See «WIRING DIAGRAMS»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style). If battery voltage is indicated, go to step 4. If battery voltage is not indicated, go to next step.
  3. Repair open in Brown wire between front temperature door actuator connector and splice S243. Splice S243 is located approximately 1.5" (4 cm) from recirculation door actuator harness breakout, toward blower relay. Go to «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check).
  4. Use a DVOM to check continuity between ground and front temperature door actuator connector terminal No. 7 (Black wire). If continuity is indicated, go to step 6. If continuity is not indicated, go to next step.
  5. Repair open in Black wire between front temperature door actuator connector and splice S244. Splice S244 is located approximately 3" (8 cm) from recirculation door actuator harness breakout, toward blower relay. Go to «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check).
  6. Turn ignition switch to ON position. Turn blower switch to low position. Ensure that front blower motor operates. Use a DVOM to measure voltage between ground and front temperature door actuator connector terminal No. 8 (Light Blue wire). Observe DVOM reading while turning temperature control knob through all settings. If voltage reading varies smoothly, go to step 9. If voltage reading is erratic and does not vary smoothly, go to next step.
  7. Disconnect A/C-heater control assembly 10-pin connector C3. Use a DVOM to measure voltage between ground and A/C-heater control assembly connector C3 cavity terminal No. 9 (control assembly side). Observe DVOM reading while turning temperature control knob through all ranges. If voltage reading varies smoothly, go to next step. If voltage reading is erratic and does not vary smoothly, go to step 10.
  8. Repair source of high resistance or short in White wire between A/C-heater control assembly and front temperature door actuator. Go to «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check).
  9. Remove temperature door actuator and ensure that door moves freely and does not bind. If door is okay, replace front temperature door actuator. See «ACTUATORS»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__removal-installation-temperature) under REMOVAL & INSTALLATION. Go to «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check).
  10. Replace A/C-heater control assembly. See «A/C-HEATER CONTROL ASSEMBLY»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style) under REMOVAL & INSTALLATION. Go to «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check).

AIR INLET ACTUATOR INOPERATIVE

  1. Perform «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check). Go to next step.
  2. Turn ignition switch to ON position. Turn blower switch to medium-low (M1) position. Depress recirculation button. With DVOM negative lead connected to ground, backprobe A/C-heater control assembly connector terminal No. 4 (Dark Green wire). See «WIRING DIAGRAMS»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style). If battery voltage is indicated, go to next step. If battery voltage is not indicated, go to step 10.
  3. Disconnect air inlet door actuator connector. (Scheme 4) Use a DVOM to measure voltage between air inlet door actuator connector terminal No. 6 (Dark Green wire) and ground. Ensure that recirculation button is depressed. If battery voltage is indicated, go to step 5. If battery voltage is not indicated, go to next step.
  4. Repair open in Dark Green wire between A/C-heater control assembly and air inlet door actuator connector. Go to «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check).
  5. Use a DVOM to measure voltage between air inlet door actuator connector terminal No. 5 (Brown wire) and ground. If battery voltage is indicated, go to step 7. If battery voltage is not indicated, go to next step.
  6. Repair open in Brown wire between air inlet door actuator connector and splice S243. Splice S243 is located approximately 1.5" (4 cm) from recirculation door actuator harness breakout, toward blower relay. Go to «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check).
  7. Use a DVOM to check continuity between air inlet door actuator connector terminal No. 7 (Black wire) and ground. If continuity is indicated, go to step 9. If continuity is not indicated, go to next step.
  8. Repair open in Black wire between air inlet door actuator connector and splice S244. Splice S244 is located approximately 3" (8 cm) from air inlet door actuator harness breakout, toward blower relay. Go to «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check).
  9. Remove air inlet door actuator and ensure that door moves freely and does not bind. If door is okay, replace air inlet actuator. Go to «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check).
  10. Disconnect A/C-heater control assembly 10-pin connector C3. Use a DVOM to measure voltage between ground and A/C-heater control assembly connector C3 terminal No. 5 (Brown wire). If battery voltage is indicated, go to next step. If battery voltage is not indicated, go to step 12.
  11. Replace A/C-heater control assembly. See «A/C-HEATER CONTROL ASSEMBLY»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style) under REMOVAL & INSTALLATION. Go to «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check).
  12. Repair open in Brown wire between A/C-heater control assembly and splice S268. Splice S268 is located approximately 2.5" (7 cm) into A/C-heater control assembly harness breakout. Go to «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check).

AUXILIARY MODE DOOR ACTUATOR INOPERATIVE

  1. Perform «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check) . Go to next step.
  2. Turn ignition switch to ON position. With DVOM negative lead connected to ground, backprobe auxiliary HVAC logic module connector terminal "F" (White wire). See «WIRING DIAGRAMS»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style) . Monitor DVOM reading while rotating front and rear auxiliary mode control knobs from upper to lower outlet settings. If voltage reading varies smoothly, go to next step. If voltage reading is erratic and does not vary smoothly, go to step 10 .
  3. Disconnect auxiliary HVAC logic module and auxiliary mode door actuator connectors. Use a DVOM to check for continuity of White wire between auxiliary HVAC logic module connector terminal "F" and auxiliary mode door actuator connector terminal No. 8. If continuity is indicated, go to step 5 . If continuity is not indicated, go to next step.
  4. Repair open in White wire between auxiliary HVAC logic module and auxiliary mode door actuator. Go to «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check) .
  5. Use a DVOM to check for continuity between ground and auxiliary mode door actuator connector terminal No. 7 (Black wire). If continuity is indicated, go to step 7 . If continuity is not indicated, go to next step.
  6. Repair open in Black wire between auxiliary mode door actuator and splice S403. Splice S403 is located approximately 2.5" (7 cm) from auxiliary blower motor resistor breakout, toward blower motor. Go to «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check) .
  7. Use a DVOM to measure voltage between ground and auxiliary mode door actuator connector terminal No. 10 (Brown wire). If battery voltage is indicated, go to step 9 . If battery voltage is not indicated, go to next step.
  8. Repair open in Brown wire between auxiliary mode door actuator and splice S400. Splice S400 is located approximately 6.5" (17 cm) from auxiliary blower motor relays breakout toward blower motor. Go to «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check) .
  9. Remove auxiliary mode door actuator and ensure that door moves freely and does not bind. If door is okay, replace auxiliary mode actuator. See «ACTUATORS»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__removal-installation-mode) under REMOVAL & INSTALLATION. Go to «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check) .
  10. Disconnect auxiliary HVAC logic module connector. Use a DVOM to measure voltage between ground and auxiliary HVAC logic module connector terminal "J" (Brown wire). If voltage is indicated, go to step 12 . If voltage is not indicated, go to next step.
  11. Repair open in Brown wire between auxiliary HVAC logic module and splice S308. Splice S308 is located approximately 2" (5 cm) from auxiliary blower relays breakout, toward blower motor. Go to «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check) .
  12. Use a DVOM to measure voltage between ground and auxiliary HVAC logic module connector terminal "E" (Light Blue wire). Rotate front auxiliary mode control knob from upper to lower outlet settings. Measure voltage between ground and auxiliary HVAC logic module connector terminal "D" (Dark Blue wire). Monitor DVOM while rotating rear auxiliary mode control knob from upper to lower outlet settings. If voltage reading varies smoothly, go to next step. If voltage reading is erratic and does not vary smoothly, go to step 14 .
  13. Replace auxiliary HVAC logic module. See «AUXILIARY A/C-HEATER CONTROL ASSEMBLY»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__removal-installation-rear-overhead-console) under REMOVAL & INSTALLATION. Go to «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check) .
  14. If terminal "E" (Light Blue wire) from front auxiliary A/C-heater control assembly, terminal "D" (Dark Blue wire) from rear auxiliary A/C-heater control assembly or both circuits are at fault, connect negative lead of DVOM to ground and backprobe front or rear auxiliary A/C-heater control assembly connector terminal "J" (Light Blue wire on front module; Dark Blue wire on rear module). Monitor DVOM reading while rotating front or rear auxiliary mode control knob from upper to lower outlet settings. If voltage reading varies smoothly, go to next step. If voltage reading is erratic and does not vary smoothly, go to step 16 .
  15. Replace suspect auxiliary A/C-heater control assembly. See «AUXILIARY A/C-HEATER CONTROL ASSEMBLIES»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style) under REMOVAL & INSTALLATION. Go to «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check) .
  16. Repair source of high resistance or short in Dark Blue wire or Light Blue wire between suspect auxiliary A/C-heater control assembly and auxiliary HVAC logic module. Go to «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check) .

AUXILIARY TEMPERATURE ACTUATOR INOPERATIVE

  1. Perform «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check) . Go to next step.
  2. Turn ignition switch to ON position. With a DVOM negative lead connected to ground, backprobe for voltage at auxiliary HVAC logic module connector terminal "B" (Dark Blue wire). See «WIRING DIAGRAMS»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style) . Monitor DVOM while adjusting front and rear auxiliary temperature controls from hot to cold. If voltage reading varies smoothly, go to next step. If voltage reading is erratic and does not vary smoothly, go to step 10 .
  3. Turn ignition switch to OFF position. Disconnect auxiliary HVAC logic module connector. Disconnect auxiliary temperature door actuator connector. Use a DVOM to check for continuity between auxiliary HVAC logic module connector terminal "B" and auxiliary temperature door actuator connector terminal No. 8 (Dark Blue wire). If continuity is indicated, go to step 5 . If continuity is not indicated, go to next step.
  4. Repair open in Dark Blue wire between auxiliary HVAC logic module and auxiliary temperature door actuator. Go to «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check) .
  5. Use a DVOM to check continuity between ground and auxiliary temperature door actuator connector terminal No. 7 (Black wire). If continuity is indicated, go to step 7 . If continuity is not indicated, go to next step.
  6. Repair open in Black wire between auxiliary temperature door actuator and S403. Splice S403 is located approximately 2.5" (7 cm) from auxiliary blower motor resistor breakout, toward blower motor. Go to «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check) .
  7. Use a DVOM to measure voltage between ground and auxiliary temperature door actuator connector terminal No. 10 (Brown wire). If battery voltage is indicated, go to step 9 . If battery voltage is not indicated, go to next step.
  8. Repair open in Brown wire between auxiliary temperature door actuator and splice S400. Splice S400 is located approximately 6.5" (17 cm) from auxiliary blower relays breakout, toward blower motor. Go to «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check) .
  9. Replace auxiliary temperature door actuator. Go to «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check) .
  10. Disconnect auxiliary HVAC logic module connector. Use a DVOM to measure voltage between ground and auxiliary HVAC logic module connector terminal "J" (Brown wire). If battery voltage is indicated, go to step 12 . If battery voltage is not indicated, go to next step.
  11. Repair open in Brown wire between auxiliary HVAC logic module and splice S308. Splice S308 is located approximately 2" (5 cm) from auxiliary blower relays breakout, toward blower motor. Go to «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check) .
  12. Use a DVOM to measure voltage between ground and auxiliary HVAC logic module connector terminal "A" (Light Blue wire). Monitor DVOM while rotating front auxiliary A/C-heater control assembly temperature control from hot to cold position. Use a DVOM to measure voltage between ground and auxiliary HVAC logic module connector terminal "C" (Dark Blue wire). Monitor DVOM while rotating rear auxiliary A/C-heater control assembly temperature control from hot to cold position. If voltage reading varies smoothly, go to next step. If voltage reading is erratic and does not vary smoothly, go to step 14 .
  13. Replace auxiliary HVAC logic module. See «AUXILIARY A/C-HEATER CONTROL ASSEMBLY»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__removal-installation-rear-overhead-console) under REMOVAL & INSTALLATION.
  14. If terminal "A" (Light Blue wire) from front auxiliary A/C-heater control assembly, terminal "C" (Dark Blue wire) from rear auxiliary A/C-heater control assembly or both circuits are at fault, connect negative lead of DVOM to ground and backprobe front or rear auxiliary A/C-heater control assembly connector terminal "H" (Light Blue wire on front module; Dark Blue wire on rear module). Monitor DVOM reading while rotating front or rear auxiliary mode control knob from upper to lower outlet settings. If voltage reading varies smoothly, go to step 16 . If voltage reading is erratic and does not vary smoothly, go to next step.
  15. Replace suspect auxiliary A/C-heater control assembly. See «AUXILIARY A/C-HEATER CONTROL ASSEMBLIES»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style) under REMOVAL & INSTALLATION. Go to «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check) .
  16. Repair source of high resistance or short in Dark Blue wire or Light Blue wire between suspect auxiliary A/C-heater control assembly and auxiliary HVAC logic module. Go to «AIR DELIVERY SYSTEM CHECK»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__air-delivery-system-check) .

A/C SYSTEM PERFORMANCE

  1. Park vehicle out of direct sunlight. Open doors or windows to ventilate vehicle. Vent exhaust system, if necessary. Connect manifold gauge set. Note ambient temperature and relative humidity. Close all doors and windows. Turn on A/C system. Set blower to high speed, and temperature lever to COLD position. Open vents.
  2. Insert thermometer into right center outlet. Place transmission in Park or Neutral. Start engine and allow it to run at 1500 RPM until outlet air reaches lowest temperature (approximately 3 minutes). See «A/C SYSTEM SPECIFICATIONS»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style) table.
Ambient Temp. °F (°C)Low-Side Pressure psi (kg/cm 2 )High-Side Pressure psi (kg/cm 2 )Air Outlet Temp. °F (°C)
80 (27)32 (2.2)228 (16)51 (10)
90 (32)39 (2.6)280 (19)59 (15)
100 (38)44 (3.0)301 (20)66 (19)
110 (43)46 (3.2)327 (22)75 (24)
(1) Specifications are with relative humidity at 40 percent.
(1)Specifications are with relative humidity at 40 percent.

A/C SYSTEM SPECIFICATIONS (1)

REMOVAL & INSTALLATION

WARNINGTo avoid injury from accidental air bag deployment, read and carefully follow all SERVICE PRECAUTIONS and DISABLING & ACTIVATING AIR BAG SYSTEM procedures in AIR BAG SYSTEM SAFETY article in GENERAL SERVICING.

Note. For non-auxiliary system blower motor removal and installation procedures, see HEATER SYSTEMS - RWD TRUCKS & VANS - EXCEPT TRACKER article.

  1. Disconnect negative battery cable. Tilt steering column to lowest position. Remove instrument panel bezel by pulling outward to disengage clips. Disconnect electrical connectors from bezel. Using a small screwdriver, release radio assembly snap-fit retainers. Disconnect electrical connectors and remove radio.
  2. Release control assembly snap-fit retainers. Pull control assembly away from instrument panel. Unplug connectors. Remove control assembly. Remove blower switch knob and retaining clip. Remove blower switch. To install, reverse removal procedure.
  1. Disconnect negative battery cable. Discharge A/C system, using approved refrigerant recovery/recycling equipment. Disconnect electrical connectors, as necessary. Remove pressure cycling switch. Disconnect accumulator lines, and cap openings. Remove accumulator bracket screws and accumulator.
  2. To install, reverse removal procedure. Add 3.5 ounces of clean refrigerant oil to new accumulator. Lightly lubricate new "O" rings with clean refrigerant oil prior to installation. Evacuate, charge, and leak test A/C system.

Removal & Installation (Mode)

Disconnect negative battery cable. Actuator is located on left side of A/C-heater assembly. (Scheme 4) Disconnect actuator electrical connectors. Remove adjuster links from control lever. Remove screws and remove actuator. To install, reverse removal procedure. Adjust actuator if necessary. See ACTUATORS under ADJUSTMENTS.

Removal & Installation (Temperature)

Disconnect negative battery cable. Actuator is located on front of A/C-heater assembly. (Scheme 4) Remove glove box. Disconnect actuator electrical connectors if necessary. Remove screws and remove actuator. To install, reverse removal procedure. Adjust actuator if necessary. See ACTUATORS under ADJUSTMENTS.

Removal & Installation (Front Overhead Console)

Disconnect negative battery cable. Remove screws attaching roof console to headliner. Remove electrical connectors from control assembly. Remove front auxiliary A/C-heater control assembly (in front overhead console) from roof console. (Scheme 2) To install, reverse removal procedure.

Removal & Installation (Rear Overhead Console)

Remove bezel. Remove rear auxiliary A/C-heater control assembly (in rear overhead console) from roof panel. (Scheme 3) Remove electrical connectors from control assembly. Auxiliary HVAC logic module is located behind opening for rear auxiliary A/C-heater control assembly. To install, reverse removal procedure.

Disconnect negative battery cable. Remove middle and rear seats if necessary. Remove passenger's rear trim panel armrest. Remove rear door pillar trim panel. Remove rear door sill cover. Remove rear trim panel by pulling upward to release clips. Unplug electrical connector and remove screws securing blower motor. (Scheme 5) On Suburban, auxiliary blower motor resistor (5) is located on underside of blower motor housing. (Scheme 6) On Escalade, Tahoe and Yukon, auxiliary blower motor resistor (1) is located on top of auxiliary A/C-heater assembly. (Scheme 7) To install, reverse removal procedure.

Scheme 5

Scheme 5: Removal & Installation
Scheme 5: Removal & Installation

Scheme 6

Scheme 6
Scheme 6

Scheme 7

Scheme 7
Scheme 7

Removal & Installation (Suburban)

  1. Disconnect negative battery cable. Discharge A/C system, using approved refrigerant recovery/recycling equipment. Remove middle and rear seats if necessary.
  2. Remove passenger's rear trim panel armrest. Remove rear door pillar trim panel. Remove rear door sill cover. Remove rear trim panel by pulling upward to release clips. Remove middle and rear seats if necessary. Remove passenger's rear trim panel armrest. Remove rear door pillar trim panel. Remove rear door sill cover. Remove rear trim panel by pulling upward to release clips.
  3. Remove right rear fender flare molding (if equipped). Disconnect heater hoses at auxiliary heater core from under vehicle. Remove inlet and outlet lines at evaporator core, and cap openings. Disconnect electrical connectors, if necessary. Remove case clip and screws. Separate case halves. Remove evaporator case cover. Remove evaporator core from case. (Scheme 5)
  4. To install, reverse removal procedure. Fill cooling system, and check for leaks. Evacuate, charge, and leak test A/C system.

Removal & Installation (Escalade, Tahoe & Yukon)

  1. Disconnect negative battery cable. Discharge A/C system, using approved refrigerant recovery/recycling equipment. Remove middle and rear seats, if necessary.
  2. Remove passenger's rear trim panel armrest. Remove rear door pillar trim panel. Remove rear door sill cover. Remove rear trim panel by pulling upward to release clips. Remove rear seat if necessary. Remove passenger's rear trim panel armrest. Remove rear door pillar trim panel. Remove rear door sill cover. Remove rear trim panel by pulling upward to release clips.
  3. Disconnect heater hoses at auxiliary heater core from under vehicle. Remove inlet and outlet lines at evaporator core, and cap openings. Disconnect electrical connectors, if necessary. Remove evaporator case from vehicle. Remove case clips and screws. Separate case halves. Remove evaporator or heater core from case. (Scheme 5)
  4. To install, reverse removal procedure. Fill cooling system, and check for leaks. Evacuate, charge, and leak test A/C system.
  1. Disconnect negative battery cable. Discharge A/C system, using approved refrigerant recovery/recycling equipment. Remove parking light assemblies and disconnect electrical connectors. Remove radiator grille. Remove radiator grille center support.
  2. Remove auxiliary cooling fan (if equipped). Disconnect condenser inlet and outlet lines, and cap openings. Bend left grille support outward for clearance. Pull condenser forward and then lower it to remove from vehicle.
  3. To install, reverse removal procedure. Lubricate new "O" rings with clean refrigerant oil prior to installation. Add one ounce of clean refrigerant oil to condenser. Evacuate, charge, and leak test A/C system.

Scheme 8

Scheme 8
Scheme 8
  1. Disconnect negative battery cable. Discharge A/C system, using approved refrigerant recovery/recycling equipment. Remove compressor drive belt. Disconnect compressor inlet and outlet lines, and cap openings. Disconnect electrical connectors, as necessary. Remove compressor. (Scheme 9), (Scheme 10) or (Scheme 11).
  2. To install, reverse removal procedure. If replacing compressor, drain and measure oil from old compressor. If less than one ounce is drained, add 2 ounces to new compressor. If more than one ounce is drained, add that amount to new compressor. Lubricate new "O" rings with clean refrigerant oil prior to installation. Evacuate, charge, and leak test A/C system.

Scheme 9

Scheme 9
Scheme 9

Scheme 10

Scheme 10
Scheme 10

Scheme 11

Scheme 11
Scheme 11

Note. Heater core may be accessible without removing A/C-heater assembly. Drain engine coolant. Remove passenger's side door sill plate and kick panel. Pull passenger's side of carpet back enough to access bolt at rear of heater case cover plate. If all heater case cover plate screws are accessible, begin procedure at step 6). If removing evaporator core, start at beginning of procedure.

  1. Disable air bag system. See AIR BAG SYSTEM SAFETY article in GENERAL INFORMATION. Remove glove box by squeezing sides together. Remove 2 instrument panel retaining bolts from glove box opening. Remove center floor duct. Remove center support bolt.
  2. On diesel models, remove Powertrain Control Module (PCM) and mounting tray. On all models, remove trim panels. Remove both kick panels. Remove blower motor cover and blower motor. See HEATER SYSTEMS - RWD TRUCKS & VANS - EXCEPT TRACKER.
  3. Remove driver's lower instrument panel cover and knee bolster. Lower steering column. Remove instrument panel left and right pivot bolts located at lower corners of instrument panel. Remove 3 screws from defroster vent near windshield. Disconnect any connectors and tilt instrument panel back far enough to access heater case. Remove coolant recovery reservoir from engine compartment.
  4. Drain engine coolant. Disconnect heater hoses at core. Disconnect inlet and outlet lines at evaporator core, and cap openings. Remove accumulator. Remove A/C-heater assembly-to-firewall screws and bolts. Remove A/C-heater assembly from vehicle.
  5. Remove 4 screws attaching evaporator case cover. Remove evaporator core from A/C-heater assembly.
  6. Remove 7 screws attaching heater case cover plate. Remove screws and bracket attaching heater core to A/C-heater assembly. (Scheme 12) Remove heater core.
  7. To install, reverse removal procedure. Torque fasteners to specification. See «TORQUE SPECIFICATIONS»(/cadillac/escalade/gmt400-1998-2000/remont/manual-hvac-system/#hvac-system-manual-old-style__torque-specifications). Replace any seals. Lubricate new "O" rings with clean refrigerant oil prior to installation. Add one ounce of clean refrigerant oil to evaporator. Evacuate, charge, and leak test A/C system. Fill cooling system. Start engine and check for leaks.

Scheme 12

Scheme 12
Scheme 12

TORQUE SPECIFICATIONS

ApplicationFt. Lbs. (N.m)
A/C Compressor Bolts37 (50)
Refrigerant Hose Fittings
Accumulator-To-Evaporator30 (41)
Compressor Assembly Bolt (1)25 (34)
Compressor-To-Accumulator30 (41)
Compressor-To-Evaporator24 (33)
Evaporator-To-Auxiliary Evaporator13 (18)
Evaporator Tube-To-Condenser18 (24)
INCH Lbs. (N.m)
Accumulator Bracket Screw53 (6)
Blower Motor Resistor Screw12 (1.4)
Blower Motor Screw15 (1.7)
Condenser Bracket Bolt40 (4.5)
Evaporator Case Screw97 (11)
Pressure Cycling Switch Fitting40 (4.5)
(1) Use new sealing washers.
(1)Use new sealing washers.

TORQUE SPECIFICATIONS

Manual A/C-Heater System Wiring Diagram ("C" & "K" Pickups, Escalade, Suburban, Tahoe & Yukon - Except Diesel). Scheme 13

Scheme 13: Manual A/C-Heater System Wiring Diagram ("C" & "K" Pickups, Escalade, Suburban, Tahoe & Yukon - Except Diesel)
Scheme 13: Manual A/C-Heater System Wiring Diagram ("C" & "K" Pickups, Escalade, Suburban, Tahoe & Yukon - Except Diesel)

Manual A/C-Heater System Wiring Diagram ("C" & "K" Pickups, Suburban, Tahoe & Yukon - Diesel). Scheme 14

Scheme 14: Manual A/C-Heater System Wiring Diagram ("C" & "K" Pickups, Suburban, Tahoe & Yukon - Diesel)
Scheme 14: Manual A/C-Heater System Wiring Diagram ("C" & "K" Pickups, Suburban, Tahoe & Yukon - Diesel)

Rear (Auxiliary) A/C-Heater System Wiring Diagram (Escalade, Suburban, Tahoe & Yukon - Except Diesel - 1 Of 2). Scheme 15

Scheme 15: Rear (Auxiliary) A/C-Heater System Wiring Diagram (Escalade, Suburban, Tahoe & Yukon - Except Diesel - 1 Of 2)
Scheme 15: Rear (Auxiliary) A/C-Heater System Wiring Diagram (Escalade, Suburban, Tahoe & Yukon - Except Diesel - 1 Of 2)

Rear (Auxiliary) A/C-Heater System Wiring Diagram (Escalade, Suburban, Tahoe & Yukon - Except Diesel - 2 Of 2). Scheme 16

Scheme 16: Rear (Auxiliary) A/C-Heater System Wiring Diagram (Escalade, Suburban, Tahoe & Yukon - Except Diesel - 2 Of 2)
Scheme 16: Rear (Auxiliary) A/C-Heater System Wiring Diagram (Escalade, Suburban, Tahoe & Yukon - Except Diesel - 2 Of 2)

Rear (Auxiliary) A/C-Heater System Wiring Diagram (Suburban, Tahoe & Yukon - Diesel - 1 Of 2). Scheme 17

Scheme 17: Rear (Auxiliary) A/C-Heater System Wiring Diagram (Suburban, Tahoe & Yukon - Diesel - 1 Of 2)
Scheme 17: Rear (Auxiliary) A/C-Heater System Wiring Diagram (Suburban, Tahoe & Yukon - Diesel - 1 Of 2)

Rear (Auxiliary) A/C-Heater System Wiring Diagram (Suburban, Tahoe & Yukon - Diesel - 2 Of 2). Scheme 18

Scheme 18: Rear (Auxiliary) A/C-Heater System Wiring Diagram (Suburban, Tahoe & Yukon - Diesel - 2 Of 2)
Scheme 18: Rear (Auxiliary) A/C-Heater System Wiring Diagram (Suburban, Tahoe & Yukon - Diesel - 2 Of 2)

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