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Heater Systems: Diagnosis Chevrolet Silverado 2500

Heater ~6066 words

TROUBLE SHOOTING

Note. Any information not covered in this article may be found in AVALANCHE, ESCALADE, SIERRA, SILVERADO, SUBURBAN, TAHOE & YUKON article in 2002 MANUAL A/C-HEATER SYSTEMS.

PRELIMINARY INSPECTION

Begin the system diagnosis by reviewing DESCRIPTION & OPERATION . Reviewing the description and operation information will help you determine the correct symptom diagnostic procedure when a malfunction exists. Reviewing the description and operation information will also help you determine if the condition described by the customer is normal operation. See SYMPTOM DIAGNOSIS in order to identify the correct procedure for diagnosing the system and where the procedure is located.

DIAGNOSTIC STARTING POINT

Begin the system diagnosis with SYMPTOM DIAGNOSIS . Review the DESCRIPTION & OPERATION information to help you determine the correct symptom diagnostic procedure when a malfunction exists. Reviewing the description and operation information will also help you determine if the condition described by the customer is normal operation.

Visual/Physical Inspection

Inspect for aftermarket devices which could affect the operation of the HVAC System. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom. Check for proper coolant level and condition. The following conditions may cause window fogging

  1. Wet carpet or mats.
  2. High humidity.
  3. Interior water leak.
  4. Maximum passenger capacity.
  5. Blocked body pressure relief valves.
  6. Inspect the air distribution system for blocked or damaged air inlet or outlet vents.

Symptom List

Refer to a SYMPTOM TESTS from the following list in order to diagnose the symptom

  1. Blower motor always on.
  2. Blower motor inoperative.
  3. Blower motor malfunction.
  4. Too hot in vehicle.
  5. Improper air delivery.
  6. High or low temperature control effort.
  7. Blower motor noise diagnosis.
  8. HVAC module noise diagnosis.

HEATER PERFORMANCE TEST

CAUTIONAvoid contact with moving parts and hot surfaces while working around a running engine in order to prevent physical injury.
  1. Were you sent here from another test? If so, go to next step. If not, see «SYMPTOM DIAGNOSIS»(ref-152575-S30430218912003021200000) under TROUBLE SHOOTING. If problem is not found in SYMPTOM DIAGNOSIS, go to next step.
  2. Start the engine. Allow the engine to idle. Does the engine reach a normal operating temperature? If so, go to next step. If not, go to step 9 .
  3. Allow to idle. Select the FLOOR mode. Select the minimum blower speed. Select the maximum temperature setting. Feel the temperature of the inlet and outlet hoses at the heater core. Does the inlet hose feel warmer than the outlet hose? If so, go to step 7 . If not, go to next step.
  4. Install a thermometer into the I/P center air outlet. Secure a thermometer to the heater core outlet hose. Select the PANEL mode. Select the maximum blower speed. Select the maximum temperature setting. Record the temperature at the following locations: The I/P center air outlet. The heater core outlet hose. Compare the recorded temperatures. Are the temperatures similar? If so, go to next step. If not, go to step 6 .
  5. Inspect and repair the following areas of the vehicle for cold air leaks: The cowl. The recirculation door (if equipped). The HVAC module case. Perform the necessary repairs. After repairs are complete, go to step 10 .
  6. Inspect the temperature door operation. Perform any necessary repairs. After repairs are complete, go to step 10 .
  7. Turn the engine off. Backflush the heater core. Start the engine. Select the FLOOR mode. Select the minimum blower speed. Select the maximum temperature setting. Feel the temperature of the inlet and outlet hoses at the heater core. Does the inlet hose feel warmer than the outlet hose? If so, go to next step. If not, go to step 10 .
  8. Replace the heater core. See «HEATER CORE»(ref-152575-S29530821172003021200000) under REMOVAL & INSTALLATION. After repairs are complete, go to step 10 .
  9. Repair the low engine temperature concern. After repairs, go to next step.
  10. Operate the system in order to verify the repair. Does the system operate correctly? If so, system is okay. If not, go to step 2 .

SYMPTOM TESTS

Note. Vehicles without air conditioning do not have electric door actuators. The manufacturer does not separate "heater only" information from air conditioned vehicle information.

Note. These following tests apply to both heater only, and air conditioned vehicles. For heater only vehicles, disregard references to air conditioning checks and procedures.

SymptomTest
Air Delivery ImproperA
Blower Always OnB
Blower Motor InoperativeC
Blower Motor MalfunctionD
Blower Motor NoiseE
HVAC Module NoiseF
Too Hot In VehicleG
High Or Low Mode Control EffortH
High Or Low Temperature Control EffortI

SYMPTOM TEST DIRECTORY

TEST A: AIR DELIVERY IMPROPER

Note. For circuit reference, see CONNECTOR IDENTIFICATION and/or WIRING DIAGRAMS .

Note. Definition: Air does not flow correctly from the air distribution outlets.

  1. Did you review the «DESCRIPTION & OPERATION»(ref-152575-S05259068492003021200000) and perform the necessary inspections? If so, go to next step. If not, see «TROUBLE SHOOTING»(ref-152575-S28811737292003021200000) .
  2. Turn the ignition on, with the engine off. Place the blower motor switch in the OFF position. Is the blower motor off? If so, go to next step. If not, go to «BLOWER MOTOR ALWAYS ON»(ref-152575-S12267330802003021200000) .
  3. Place the blower motor switch in each speed position. Does the blower motor operate at all? If so, go to next step. If not, go to «BLOWER MOTOR INOPERATIVE»(ref-152575-S38723874672003021200000) .
  4. Does the blower motor operate in each speed position? If so, go to next step. If not, go to «BLOWER MOTOR MALFUNCTION»(ref-152575-S10442171572003021200000) .
  5. Is the HVAC control assembly inoperative in all positions? If so, go to next step. If not, go to step 16 .
  6. Observe the drive shaft of mode actuator. Place the mode control in each mode position. Does the mode actuator drive shaft rotate for each selected position? If so, go to next step. If not, go to step 8 .
  7. Inspect the mode door and the mode actuator for the following conditions: Misaligned mode actuator. Broken linkages or binding linkages. A broken mode door or a binding mode door. An obstruction that prevents the mode door from operating within the full range of motion. Did you find and correct the condition? If so, go to step 23 . If not, problem is intermittent. See «TROUBLE SHOOTING»(ref-152575-S28811737292003021200000) .
  8. Check the ignition voltage circuit of the mode actuator for an open or for a high resistance. Did you find and correct the condition? If so, go to step 23 . If not, go to next step.
  9. Check the ground circuit of the mode actuator for an open or high resistance. Did you find and correct the condition? If so, go to step 23 . If not, go to next step.
  10. Check the 5 volt reference circuit of the mode actuator for a short to ground, short to voltage, high resistance or an open. Did you find and correct the condition? If so, go to step 23 . If not, go to next step.
  11. Check the signal circuit of the mode door actuator for a short to ground, short to voltage, high resistance or an open. Did you find and correct, the condition? If so, go to step 23 . If not, go to next step.
  12. Check the mode door control circuit of the mode actuator for a short to ground, short to voltage, high resistance or an open. Did you find and correct the condition? If so, go to step 23 . If not, go to next step.
  13. Turn the ignition on, with the engine off. Backprobe and monitor the voltage from the signal circuit of the mode door actuator with a test light that is connected to ground. Connect a 3-ampere fused jumper between the mode door control circuit and the 5 volt reference circuit of the mode actuator. This action drives the motor to FLOOR mode. Remove and reconnect the jumper between the mode door control circuit and the ground circuit of the mode actuator. This action drives the motor to DEF mode. Does the mode actuator drive shaft rotate and does the voltage change? If so, go to next step. If not, go to step 18 .
  14. Backprobe the mode actuator connector terminal in order to measure the voltage from the mode door control circuit to ground. Place the mode control in each mode position. Is the voltage measurement near: Zero volts toward defrost. 5 Volts toward floor. 2.5 volts stationary. If so, go to next step. If not, go to step 20 .
  15. Repair the mode door for a mechanical condition or for a condition that allows excessive travel to the door. After repairs are complete, go to step 23 .
  16. Check the ignition voltage circuit of the HVAC controller for an open, for a high resistance or for a short to ground. Did you find and correct the condition? If so, go to step 23 . If not, go to next step.
  17. Check the ground circuit of the HVAC controller for an open. Did you find and correct the condition? If so, go to step 23 . If not, go to step 20 .
  18. Inspect for bad connections at the harness connector of the mode actuator. Did you find and correct the condition? If so, go to step 23 . If not, go to next step.
  19. Inspect the mode door and any attaching linkage for any binding. Inspect the ducts for any debris that would prevent airflow through the ducts. Did you find and correct the condition? If so, go to step 23 . If not, go to step 21 .
  20. Inspect for poor connections at the harness connector of the HVAC control assembly. Did you find and correct the condition? If so, go to step 23 . If not, go to step 22 .
  21. Replace the mode actuator. See «MODE DOOR ACTUATOR»(ref-152575-S42004335142003021200000) under REMOVAL & INSTALLATION. After repairs are complete, go to step 23 .
  22. Replace the HVAC control assembly. See «HVAC CONTROL ASSEMBLY»(ref-152575-S00895000392003021200000) under REMOVAL & INSTALLATION. After repairs are complete, go to step 23 .
  23. Operate the system in order to verify the repair. Did you correct the condition? If so, system is okay. If not, go to step 2 .

TEST B: BLOWER MOTOR ALWAYS ON

Note. For circuit reference, see CONNECTOR IDENTIFICATION and/or WIRING DIAGRAMS .

Note. Definition: The blower motor is ON while the blower motor switch is in the OFF position.

  1. Did you review the «DESCRIPTION & OPERATION»(ref-152575-S05259068492003021200000) and perform the necessary inspections? If so, go to next step. If not, see «TROUBLE SHOOTING»(ref-152575-S28811737292003021200000) .
  2. Turn the ignition on, with the engine off. Place the mode switch in the OFF position. Is the blower motor off? If so, condition is intermittent. See «SYMPTOM DIAGNOSIS»(ref-152575-S30430218912003021200000) under TROUBLE SHOOTING.
  3. Turn the ignition off. Disconnect the connector "C1" to the blower motor resistor assembly. Turn the ignition on, with the engine off. Probe each blower motor control circuit with a test light that is connected to ground. Did the test light illuminate while connected to any of the blower motor control circuits? If so, go to next step. If not, go to step 5 .
  4. Check the appropriate blower motor control circuit for a short to voltage. Did you find and correct the condition? If so, go to step 9 . If not, go to step 6 .
  5. Inspect for bad connections at the harness connectors of the blower motor resistor assembly. Did you find and correct the condition? If so, go to step 9 . If not, go to step 7 .
  6. Inspect for bad connections at the harness connector of the HVAC control assembly. Did you find and correct the condition? If so, go to step 9 . If not, go to step 8 .
  7. Replace the blower motor resistor assembly. See «BLOWER MOTOR RESISTOR»(ref-152575-S40726907602003021200000) under REMOVAL & INSTALLATION. Did you complete the replacement? After repairs are complete, go to step 9 .
  8. Replace the HVAC control assembly. See «HVAC CONTROL ASSEMBLY»(ref-152575-S00895000392003021200000) under REMOVAL & INSTALLATION. After repairs are complete, go to step 9 .
  9. Operate the system in order to verify the repair. Did you correct the condition? If so, system is okay. If not, go to step 2 .

TEST C: BLOWER MOTOR INOPERATIVE

Note. For circuit reference, see CONNECTOR IDENTIFICATION and/or WIRING DIAGRAMS .

Note. Definition: The blower motor is inoperative in all speed positions.

  1. Did you review the «DESCRIPTION & OPERATION»(ref-152575-S05259068492003021200000) and perform the necessary inspections? If so, go to next step. If not, see «TROUBLE SHOOTING»(ref-152575-S28811737292003021200000) .
  2. Turn the ignition on, with the engine off. Place the mode switch in the vent position. Place the blower motor switch in each speed position. Does the blower motor operate in each speed position? If so, problem is intermittent. See «TROUBLE SHOOTING»(ref-152575-S28811737292003021200000) . If not, go to next step.
  3. Turn the ignition off. Disconnect the blower motor. Turn the ignition on, with the engine off. Connect a test light between the blower motor supply voltage circuit and ground. Place the blower motor switch in the minimum speed position. Does the test light illuminate? If so, go to next step. If not, go to step 5 .
  4. Connect a test light between the blower motor supply circuit and the blower motor ground circuit. Place the blower motor switch in the minimum speed position. Does the test light illuminate? If so, go to step 9 . If not, go to step 8 .
  5. Turn the ignition off. Disconnect the connector "C1" at the blower motor resistor assembly. Turn the ignition on, with the engine off. Place the blower motor switch in the LOW speed position. Probe the control circuit of the low blower motor with a grounded test light. Does the test light illuminate? If so, go to step 10 . If not, go to next step.
  6. Check the ignition voltage circuit of the HVAC module for an open, for a high resistance, or for a short to ground. Did you find and correct the condition? If so, go to step 15 . If not, go to next step.
  7. Check each blower motor control circuit for a short to ground. Did you find and correct the condition? If so, go to step 15 . If not, go to step 11 .
  8. Check the ground circuit of the blower motor resistor assembly for an open or high resistance. Did you find and correct the condition? If so, go to step 15 . If not, go to step 10 .
  9. Inspect for bad connections at the harness connector of the blower motor. Did you find and correct the condition? If so, go to step 15 . If not, go to step 13 .
  10. Inspect for bad connections at the harness connectors of the blower motor resistor assembly. Did you find and correct the condition? If so, go to step 15 . If not, go to step 14 .
  11. Inspect for bad connections at the harness connectors of the HVAC control assembly. Did you find and correct the condition? If so, go to step 15 . If not, go to next step.
  12. Replace the HVAC control assembly. See «HVAC CONTROL ASSEMBLY»(ref-152575-S00895000392003021200000) under REMOVAL & INSTALLATION. After repairs are complete, go to step 15 .
  13. Replace the blower motor. See «BLOWER MOTOR & FAN»(ref-152575-S28878035422003021200000) under REMOVAL & INSTALLATION. After repairs are complete, go to step 15 .
  14. Replace blower motor resistor assembly. See «BLOWER MOTOR RESISTOR»(ref-152575-S40726907602003021200000) under REMOVAL & INSTALLATION. After repairs are complete, go to step 15 .
  15. Operate the system in order to verify the repair. Did you correct the condition? If so, system is okay. If not, go to step 2 .

TEST D: BLOWER MOTOR MALFUNCTION

Note. For circuit reference, see CONNECTOR IDENTIFICATION and/or WIRING DIAGRAMS .

Note. Definition: The blower motor operates in at least one, but not all, speed positions.

  1. Did you review the «DESCRIPTION & OPERATION»(ref-152575-S05259068492003021200000) and perform the necessary inspections? If so, go to next step. If not, see «TROUBLE SHOOTING»(ref-152575-S28811737292003021200000) .
  2. Turn the ignition on, with the engine off. Place the mode control in the VENT position. Place the blower motor switch in each speed position. Does the blower motor operate in each speed position? If so, go to next step. If not, problem is intermittent. See «TROUBLE SHOOTING»(ref-152575-S28811737292003021200000) .
  3. Turn the ignition off. Disconnect the connector "C1" at the blower motor resistor assembly. Turn the ignition on, with the engine off. Check the battery voltage circuit of the blower motor resistor assembly with a test light that is connected to ground. Does the test light illuminate? If so, go to next step. If not, go to step 6 .
  4. Turn the ignition off. Disconnect the connector "C1" at the blower motor resistor assembly. Turn the ignition on, with the engine off. Check each blower motor control circuit with a test light that is connected to ground. Place the blower motor switch in the appropriate speed position for the control circuit being tested. Does the test light illuminate in each speed position? If so, go to next step. If not go to step 7 .
  5. Turn the ignition off. Connect connector "C1" of the blower motor resistor assembly. Disconnect the blower motor. Turn the ignition on, with the engine off. Check the voltage circuit of the blower motor with a grounded test light. Place the blower motor switch in each speed position. Does the test light illuminate in each speed position? If so, go to step 8 . If not, go to step 9 .
  6. Repair the battery voltage circuit to the blower motor resistor assembly for an open or for a short to ground. After repairs are complete, go to step 11 .
  7. Check the appropriate blower motor control circuit for an open. Did you find and correct the condition? If so, go to step 11 . If not, go to step 10 .
  8. Replace the blower motor. See «BLOWER MOTOR & FAN»(ref-152575-S28878035422003021200000) under REMOVAL & INSTALLATION. After repairs are complete, go to step 11 .
  9. Replace the blower motor resistor assembly. See «BLOWER MOTOR RESISTOR»(ref-152575-S40726907602003021200000) under REMOVAL & INSTALLATION. After repairs are complete, go to step 11 .
  10. Replace the HVAC control assembly. See «HVAC CONTROL ASSEMBLY»(ref-152575-S00895000392003021200000) under REMOVAL & INSTALLATION. After repairs are complete, go to next step.
  11. Operate the system in order to verify the repair. Did you correct the condition? If so, system is okay. If not, go to step 2 .

TEST E: BLOWER MOTOR NOISE

Note. Definition: Noise originating from the blower motor.

  1. Were you sent here from SYMPTOM DIAGNOSIS? If so, go to next step. If not, go to «SYMPTOM DIAGNOSIS»(ref-152575-S30430218912003021200000) under TROUBLE SHOOTING.
  2. Sit inside the vehicle. Close the vehicle doors and windows. Turn the ignition on, with the engine off. Cycle the blower motor through all of the speeds and modes in order to determine where and when the noise occurs. Is a noise evident during the blower operation? If so, go to next step. If not, go to step 11 .
  3. Does the noise vary with the blower speed? If so, go to next step. If not, go to step 11 .
  4. Inspect for excessive vibration at each blower motor speed by feeling the blower case. Is excess vibration present? If so, go to next step. If not, go to step 11 .
  5. Listen to the blower motor at each speed. Is the blower motor making a squeaking or chirping noise? If so, go to step 9 . If not, go to step 11 .
  6. Remove the blower motor. See «BLOWER MOTOR & FAN»(ref-152575-S28878035422003021200000) under REMOVAL & INSTALLATION. Inspect the blower motor for deposits of foreign material. Did you find any foreign material on the blower motor? If so, go to step 8 . If not, go to next step.
  7. Inspect the blower motor for the following conditions: Cracked Blades A Loose Impeller Retainer Improper Impeller Alignment Did you find any of these conditions? If so, go to step 9 . If not, go to step 10 .
  8. Remove the foreign material. After repairs, go to step 11 .
  9. Replace the blower motor. See «BLOWER MOTOR & FAN»(ref-152575-S28878035422003021200000) under REMOVAL & INSTALLATION. After repairs, go to step 11 .
  10. Install the blower motor. See «BLOWER MOTOR & FAN»(ref-152575-S28878035422003021200000) under REMOVAL & INSTALLATION. After repairs, go to step 11 .
  11. Operate the system in order to verify the repair. Does the system operate correctly? If so, system is okay. If not, go to step 2 .

TEST F: HVAC MODULE NOISE

  1. Were you sent here from SYMPTOM DIAGNOSIS? If so, go to next step. If not, go to «SYMPTOM DIAGNOSIS»(ref-152575-S30430218912003021200000) under TROUBLE SHOOTING.
  2. Start the engine. Cycle through all of the following: Blower Motor Speeds HVAC Modes Temperature Control Settings Determine the type of noise. Scrape, pop, tick/click, chirp or groaning or air rush/whistle Is a scrape or pop noise evident when selecting modes or temperature settings? If so, go to step 6 . If not, go to next step.
  3. Is a tick/click, chirping, groaning or scraping noise present, but decreases as blower motor speed is decreased? If so, go to step 6 . If not, go to next step.
  4. Is an air rush/whistle noise evident in all modes but not all temperature settings? If so, go to step 6 . If not, go to next step.
  5. Is an air rush/whistle noise evident only in defrost or floor mode? If so, go to next step. If not, go to next step.
  6. Remove the Instrument Panel (I/P) carrier. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. After removal, go to next step.
  7. Inspect the air flow doors for proper operation. Inspect the ducts for obstructions or foreign materials. Were any of these conditions found? If so, go to step 10 . If not, go to next step.
  8. Inspect the mode and temperature doors and seals for warping or cracking. Are the doors in normal condition? If so, go to next step. If not, go to step 12 .
  9. Replace the appropriate door and/or seals. See «REMOVAL & INSTALLATION»(ref-152575-S01233344542003021200000) . After repairs, go to step 11 .
  10. Remove any obstructions or foreign material found. After repairs, go to step 11 .
  11. Install the I/P carrier. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. After repairs, go to step 12 .
  12. Operate the system to verify the repair. Is the noise gone? If so, system is okay. If not, go to step 2 .

TEST G: TOO HOT IN VEHICLE

Note. For circuit reference, see CONNECTOR IDENTIFICATION and/or WIRING DIAGRAMS .

Note. Vehicles without air conditioning do not have electric door actuators. The manufacturer does not separate "heater only" information from air conditioned vehicle information.

Note. This test applies to heater only and air conditioned vehicles. For heater only vehicles, disregard references to air conditioning checks and procedures.

Note. Definition: The temperature can not be adjusted, or the cooling is insufficient during A/C operation.

  1. Were you sent here from «SYMPTOM DIAGNOSIS»(ref-152575-S30430218912003021200000) ? If so, go to next step. If not, go to «SYMPTOM DIAGNOSIS»(ref-152575-S30430218912003021200000) under TROUBLE SHOOTING.
  2. Turn the ignition on, with the engine off. Place the mode switch in any position except OFF. Place the blower motor switch in each speed position. Does the blower motor operate at all? If so, go to next step. If not, go to «TEST C: BLOWER MOTOR INOPERATIVE»(ref-152575-S38723874672003021200000) .
  3. Does the blower motor operate correctly for each speed position? If so, go to next step. If not, See «TEST D: BLOWER MOTOR MALFUNCTION»(ref-152575-S10442171572003021200000) .
  4. Is the HVAC control assembly inoperative? If so, go to step 18 . If not, go to next step.
  5. Does the concern occur when A/C cooling is desired? If so, go to next step. If not, go to step 8 .
  6. Start the engine. Place the blower motor switch in the maximum speed position. Place the A/C request switch in the ON position. Place the air temperature switch in the coldest position. Does the A/C compressor operate? If so, go to next step. If not, see HVAC Compressor Clutch Does Not Engage in «AVALANCHE, ESCALADE, SIERRA, SILVERADO, SUBURBAN, TAHOE & YUKON»(ref-131951) article in MANUAL A/C-HEATER SYSTEMS.
  7. Perform the refrigerant system performance test. See A/C PERFORMANCE TEST IN «AVALANCHE, ESCALADE, SIERRA, SILVERADO, SUBURBAN, TAHOE & YUKON»(ref-131951) article in MANUAL A/C-HEATER SYSTEMS. Did you find and correct the condition? If so, go to step 25 . If not, go to next step.
  8. Observe the drive shaft of the air temperature actuator. Adjust the air temperature switch. Does the drive shaft of the air temperature actuator ever rotate? If so, go to next step. If not, go to step 10 .
  9. Inspect the air temperature door and the air temperature actuator for the following conditions: A misaligned air temperature actuator. A broken air temperature door or a binding air temperature door. An obstruction that prevents air temperature door from operating within the full range of motion. Missing seals to the air temperature door. Misaligned seals to the air temperature door. Did you find and correct the condition? If so, go to step 25 . If not, problem is intermittent. See «TROUBLE SHOOTING»(ref-152575-S28811737292003021200000) .
  10. Check the ignition voltage circuit of the air temperature actuator for an open or for a high resistance. Did you find and correct the condition? If so, go to step 25 . If not, go to next step.
  11. Check the ground circuit of the air temperature actuator for an open. Did you find and correct the condition? If so, go to step 25 . If not, go to next step.
  12. Check the 5 volt reference circuit of the air temperature actuator for a high resistance. Did you find and correct the condition? If so, go to step 25 . If not, go to next step.
  13. Check the signal circuit of the air temperature door actuator an open or a high resistance. Did you find and correct the condition? If so, go to step 25 . If not, go to next step.
  14. Check the door control circuit of the air temperature actuator an open or a high resistance. Did you find and correct the condition? If so, go to step 25 . If not, go to next step.
  15. Turn the ignition on, with the engine off. Backprobe and monitor the voltage from the door signal circuit of the air temperature actuator to a good ground. Connect a 3-ampere fused jumper between the door control circuit and the 5 volt reference circuit of the air temperature actuator. This action drives the actuator to the full cool mode. Remove and reconnect the jumper wire between the air temperature door control and the ground circuit of the air temperature actuator. This action drives the actuator to the full hot mode. Does the drive shaft of the air temperature actuator rotate and does the voltage change? If so, go to next step. If not, go to step 20 .
  16. Backprobe the connector terminal of the air temperature actuator in order to measure the voltage from the door control circuit to ground. Adjust the air temperature switch. Is the voltage measurement near the specified value in each condition? Zero Volts Increasing 5 Volts Decreasing 2.5 Volts Stationary If so, go to next step. If not, go to step 22 .
  17. Repair the air temperature door for a mechanical condition or for a condition that allows excessive travel of the door. After repairs, go to step 25 .
  18. Check the ignition voltage circuit of the HVAC control assembly for an open, for a high resistance, or for a short to ground. Did you find and correct the condition? If so, go to step 25 . If not, go to next step.
  19. Check the ground circuit of the HVAC control assembly for an open. Did you find and correct the condition? Did you find and correct the condition? If so, go to step 25 . If not, go to step 22 .
  20. Inspect for poor connections at the harness connector of the air temperature actuator. Did you find and correct the condition? If so, go to step 25 . If not, go to next step.
  21. Inspect the air temperature actuator, the door, and any attaching linkage for binding or for a condition that prevents drive shaft rotation. Did you find and correct the condition? If so, go to step 25 . If not, go to step 23 .
  22. Inspect for poor connections at the harness connector of the HVAC control assembly. Did you find and correct the condition? If so, go to step 25 . If not, go to step 24 .
  23. Replace the air temperature cable (temperature actuator on trucks with air conditioning). See «TEMPERATURE DOOR CABLE»(ref-152575-S33446540972003021300000) under REMOVAL & INSTALLATION. After repairs, go to step 25 .
  24. Replace the HVAC control assembly. See «HVAC CONTROL ASSEMBLY»(ref-152575-S00895000392003021200000) under REMOVAL & INSTALLATION. After repairs, go to step 25 .
  25. Operate the system in order to verify the repair. Did you correct the condition? If so, system is okay. If not, go to step 2 .

TEST H: HIGH OR LOW MODE CONTROL EFFORT

  1. Were you sent here from SYMPTOM DIAGNOSIS? If so, go to next step. If not, go to «SYMPTOM DIAGNOSIS»(ref-152575-S30430218912003021200000) under TROUBLE SHOOTING.
  2. Is one of the following a concern of the customer: The mode control operates with little or no resistance. The HVAC outlet air is constant, regardless of the mode control setting. While driving the vehicle the mode control setting changes. Does the mode control operate too freely? If so, go to next step. If not, go to step 7 .
  3. With the ignition switch in the ON position, select high blower motor speed, cycle the mode control through all of the settings. Does the air outlet change through all of the modes? If so, go to step 16 . If not, go to next step.
  4. Inspect the connections of the mode control cable. Is the mode control cable disconnected from the mode actuator? If so, go to step 15 . If not, go to next step.
  5. Inspect the mode control cable and linkage, while operating the mode controls. Does the mode actuator move while operating the mode controls? If so, go to step 21 . If not, go to next step.
  6. Inspect the cable casing while operating the mode controls. Does the cable casing move, instead of the cable, while operating the mode controls? If so, go to step 18 . If not, go to step 21 .
  7. Inspect the HVAC control assembly for any debris or obstructions that would increase the effort to operate the mode controls. Are there any obstructions? If so, go to step 20 . If not, go to next step.
  8. Disconnect the mode control cable from the mode actuator. Operate the HVAC control assembly with the mode control cable disconnected. Does the HVAC control assembly bind now? If so, go to step 10 . If not, go to next step.
  9. With the mode control cable disconnected, manually operate the mode actuator. Inspect for binding. Does the mode actuator bind with the cable disconnected? If so, go to step 19 . If not, go to next step.
  10. Disconnect the mode control cable from the HVAC control assembly. Operate the HVAC control assembly with the cable disconnected. Does the HVAC control assembly bind now? If so, go to step 16 . If not, go to next step.
  11. With the mode control cable disconnected at both ends, extend the cable in both directions. Inspect the cable for binding. Does the mode control cable bind? If so, go to step 17 . If not, go to next step.
  12. Inspect the mode control cable for kinks or bends from incorrect routing. Repair the cable or routing as necessary. Does the mode cable still bind? If so, go to step 17 . If not, go to next step.
  13. Operate the HVAC control assembly with the mode control cable disconnected. Does the HVAC control assembly bind now? If so, go to step 16 . If not, go to next step.
  14. Reassemble the mode control system. After repairs are complete, go to step 21 .
  15. Reconnect the mode control cable to the mode actuator linkage install the cable retainers. After repairs are complete, go to step 21 .
  16. Replace the HVAC control assembly. See «HVAC CONTROL ASSEMBLY»(ref-152575-S00895000392003021200000) under REMOVAL & INSTALLATION. After repairs are complete, go to step 21 .
  17. Replace the mode control cable. See «MODE CONTROL CABLE»(ref-152575-S23464217332003021300000) under REMOVAL & INSTALLATION. After repairs are complete, go to step 21 .
  18. Secure the mode control cable casing. See «MODE CONTROL CABLE»(ref-152575-S23464217332003021300000) under REMOVAL & INSTALLATION. After repairs are complete, go to step 21 .
  19. Repair the binding door. See appropriate procedure under «REMOVAL & INSTALLATION»(ref-152575-S01233344542003021200000) . After repairs are complete, go to step 21 .
  20. Remove the debris. After repairs are complete, go to step 21 .
  21. Operate the system in order to verify the repair. Does the system operate correctly? If so, system is okay. If not, go to step 2 .

TEST I: HIGH OR LOW TEMPERATURE CONTROL EFFORT

  1. Were you sent here from SYMPTOM DIAGNOSIS? If so, go to next step. If not, go to «SYMPTOM DIAGNOSIS»(ref-152575-S30430218912003021200000) under TROUBLE SHOOTING.
  2. Is one of the following a concern of the customer: The mode control operates with little or no resistance. The HVAC outlet air is constant, regardless of the mode control setting. While driving the vehicle the mode control setting changes. Does the mode control operate too freely? If so, go to next step. If not, go to step 7 .
  3. With the ignition in the ON position, select the High blower motor speed position. Cycle the mode control through all of the settings. Does the air outlet change through all of the modes? If so, go to step 16 . If not, go to next step.
  4. Inspect the connections of the mode control cable. Is the mode control cable disconnected from the mode actuator? If so, go to step 15 . If not, go to next step.
  5. Inspect the mode control cable and linkage, while operating the mode controls. Does the mode actuator move while operating the mode controls? If so, go to step 21 . If not, go to next step.
  6. Inspect the cable casing while operating the mode controls. Does the cable casing move, instead of the cable, while operating the mode controls? If so, go to step 18 . If not, go to step 21 .
  7. Inspect the HVAC control assembly for any debris or obstructions that would increase the effort to operate the mode controls. Are there any obstructions? If so, go to step 20 . If not, go to next step.
  8. Disconnect the mode control cable from the mode actuator. Operate the HVAC control assembly with the mode control cable disconnected. Does the HVAC control assembly bind now? If so, go to step 10 . If not, go to next step.
  9. With the mode control cable disconnected: Manually operate the mode actuator. Inspect for binding. Does the mode actuator bind with the cable disconnected? If so, go to step 19 . If not, go to next step.
  10. Disconnect the mode control cable from the HVAC control assembly. Operate the HVAC control assembly with the cable disconnected. Does the HVAC control assembly bind now? If so, go to step 16 . If not, go to next step.
  11. With the mode control cable disconnected at both ends, extend the cable in both directions. Inspect the cable for binding. Does the mode control cable bind? If so, go to step 17 . If not, go to next step.
  12. Inspect the mode control cable for kinks or bends from incorrect routing. Repair the cable or routing as necessary. Does the mode cable still bind? If so, go to step 17 . If not, go to next step.
  13. Operate the HVAC control assembly with the mode control cable disconnected. Does the HVAC control assembly bind now? If so, go to step 14 . If not, go to next step.
  14. Reassemble the mode control system. After repairs are complete, go to step 21 .
  15. Reconnect the mode control cable to the mode actuator linkage install the cable retainers. After repairs are complete, go to step 21 .
  16. Replace the HVAC control assembly. See «HVAC CONTROL ASSEMBLY»(ref-152575-S00895000392003021200000) under REMOVAL & INSTALLATION. After repairs are complete, go to step 21 .
  17. Replace the mode control cable. See «MODE CONTROL CABLE»(ref-152575-S23464217332003021300000) under REMOVAL & INSTALLATION. After repairs are complete, go to step 21 .
  18. Secure the mode control cable casing. See «MODE CONTROL CABLE»(ref-152575-S23464217332003021300000) under REMOVAL & INSTALLATION. After repairs are complete, go to step 21 .
  19. Repair the binding door. Repair the appropriate door. See «REMOVAL & INSTALLATION»(ref-152575-S01233344542003021200000) . After repairs are complete, go to step 21 .
  20. Remove the debris and reassemble. After repairs are complete, go to step 21 .
  21. Operate the system in order to verify the repair. Does the system operate correctly? If so, system is okay. If not, go to step 2 .

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