A/c-Heater System - Automatic Ford Crown Victoria I

A/C SYSTEM SPECIFICATIONS

A/C SYSTEM SPECIFICATIONS

DESCRIPTION

The Automatic Temperature Control (ATC) system controls temperature and blower speed while reducing humidity of air inside vehicle. The system uses a reheat method of air conditioning in which all air-flow from blower passes through evaporator core. Temperature is regulated by reheating cooled air to desired setting.

Outlet air temperature is varied by temperature blend door, which controls amount of cooled air flowing through and/or around heater core. Reheated air is then mixed with cooled air and directed into distribution plenum. The air is then diverted to heater ducts, defroster nozzles and air conditioning registers as determined by function selector lever position.

Control Module

System temperature control is accomplished by a control module containing a microprocessor. Control module is mounted on top of control panel assembly. (Scheme 1)

Inputs to control module include in-car temperature sensor, ambient temperature sensor, control panel blower switch and temperature and function lever settings. These inputs are used to determine blend door position (through direct current actuator motor) and variable blower speed. When vacuum selector valve is in floor position, blower operation is controlled by thermal blower lock-out switch.

Note. Control module is grounded behind right trim panel.

Scheme 1

Control Panel

The control panel consists of control module, function selector, blower switch and temperature control. (Scheme 2)

The function selector consists of a vacuum selector valve and 3 internal electrical switches. The vacuum selector valve directs vacuum signals to vacuum actuators. (Scheme 1) These actuators direct airflow through the system. The vacuum selector also connects vacuum from thermal blower lock-out switch relay to outside/recirculated air door in FLOOR mode. The electrical switches control power supply to control module and A/C clutch.

Scheme 2

OFF

In this mode, outside/recirculated air door is in recirculation position. Panel doors do not receive vacuum, and floor/defrost door is in floor position. Blower is off and blend door stays in position it was in when system was last turned off.

MAX A/C

The outside/recirculated air door goes to recirculation position. Air is drawn from passenger compartment and through evaporator core. As interior temperature approaches selected temperature, blend door will move to direct air to heater core. The blend door moves to maintain interior temperature at selected level.

Note. A/C compressor will not operate when outside temperature is less than 50°F (10°C).

NORM A/C

The outside/recirculated air door moves to outside air position. Air is drawn through cowl vent, and system performs in same manner as in MAX A/C mode.

VENT

Outside air is directed through dash panel registers with automatic control of discharge air temperature. Refrigerated cooling is not available as compressor is not engaged.

FLOOR

With control lever in FLOOR position and interior temperature below temperature setting, blower operation is delayed by the thermal blower lock-out until engine coolant reaches about 120°F (49°C).

When blower turns on, outside air is directed through evaporator core to heater core. The blend door then directs airflow through heater core to floor ducts. Some air is directed to defroster ducts. The compressor does not operate in FLOOR mode.

As less heat is required to maintain interior temperature, blend door moves to direct only a portion of air from evaporator core to heater core.

DEF/FLR

In DEF/FLR (defrost/floor) mode, panel doors move to defrost position. The floor/defrost door moves to mid-position so outside air is divided between defroster outlets and floor outlets. Compressor will not operate if outside temperature is less than 50°F (10°C).

DEF

Dash panel doors and floor/defrost door are in full defrost position. All incoming air is directed to defroster outlets with some air bled to floor ducts. The blend door modulates temperature in this mode, but maximum heat can be obtained by moving temperature lever to highest temperature position. The A/C compressor operates to dehumidify air and reduce windshield fogging if ambient air temperature is 50°F (10°C).

Automatic Temperature Control Sensor

On Crown Victoria, sensor is located behind instrument panel, above radio. On Grand Marquis, sensor is located behind instrument panel, directly above A/C control panel and clock. (Scheme 3) The sensor contains a thermistor whose resistance varies with temperature. The thermistor provides an input to control module.

The sensor also includes an aspirator tube and a foam inlet seal. The aspirator provides a very small vacuum to draw a continuous sampling of passenger compartment air across thermistor. Forced air is routed to sensor through a tube from blower stream, giving power to operate aspirator.

Scheme 3

Ambient Temperature Sensor

The ambient temperature sensor is located in front of condenser, on hood latch support. (Scheme 4) The sensor contains a thermistor whose resistance varies with temperature. The thermistor measures outside air temperature and sends this signal to control module.

Scheme 4

BLEND DOOR ACTUATOR

The blend door actuator is a small electric motor, mounted on top of the plenum assembly. The actuator controls blend door movement based on electrical signals from control module. A separate feedback potentiometer feeds blend door position data to control module. The blend door controls mixing of hot and cool air to maintain pre-selected interior temperature.

BLOWER CONTROLS

Note. Temperature control lock-out valve and switch may also be referred to as the Thermal Blower Lock-Out (TBLO) switch.

Temperature Control Lock-Out Valve & Switch

The temperature control lock-out valve and switch is a combination vacuum valve and single-pole, single-throw switch. Switch is located on heater inlet hose in engine compartment. (Scheme 5) The thermal element of switch contacts coolant.

When function lever is in FLOOR position and engine is cold, blower cannot operate and outside/recirculated air door is held in recirculation position. When coolant temperature reaches about 120°F (49°C), electrical switch contacts close, allowing blower operation and outside/recirculated air door to move to outside air position.

Scheme 5

Blower Motor Speed Controller & High Blower Relay

This component converts low current electrical signals from control module to a high current, variable ground feed to blower motor. Blower motor speed is infinitely variable and is controlled by control module.

A delay function allows a gradual increase or decrease in blower motor speed under all operating conditions. When control module signals the blower motor speed controller for maximum blower speed, a relay by-passes the controller. This provides a direct ground circuit for blower motor. High blower relay, located in evaporator assembly, is accessible from engine compartment. (Scheme 6)

Note. To prevent damage to blower motor speed controller, DO NOT operate system with blower motor disconnected.

Blower Motor Ground Side Switching

Blower motor is wired in the electrical circuit between fuse panel and blower motor speed controller, allowing the controller to regulate blower motor ground circuit.

Scheme 6

COMPRESSOR CONTROLS

When a mode is selected on control panel which would allow compressor clutch operation, the compressor signal must first go through the clutch cycling pressure switch. This switch signals engine Electronic Control Assembly (ECA).

The ECA controls ground path for A/C compressor cut-out relay. The ECA disengages compressor clutch during Wide Open Throttle (WOT) operation. WOT is monitored by ECA through throttle position sensor.

Clutch Cycling Pressure Switch

This switch prevents evaporator icing during normal A/C operation. Mounted on outlet side of evaporator, the switch controls current flow to compressor clutch relay.

The clutch cycling pressure switch also prevents compressor operation during cold weather. When ambient temperature is low, refrigerant pressure is also reduced. This opens pressure switch, preventing compressor operation. This low pressure feature also protects system when refrigerant level is low.

High Pressure Relief Valve

This valve, located in compressor high side discharge line, relieves excessively high pressures. Valve opens at 450 psi (32 kg/cm 2 ) to prevent damage to compressor and other A/C components. Valve closes when pressure returns to normal.

FIXED ORIFICE TUBE CYCLING CLUTCH EVALUATION. Scheme 7

INSUFFICIENT OR NO A/C COOLING

1. Verify Condition Check A/C system operation. Ensure refrigerant pressure is greater than 50 psi (3.5 kg/cm 2 ). If system cools properly, no problem is indicated at this time. If system does not cool properly, go to next step.
2. Check A/C Compressor Clutch If A/C compressor clutch engages, go to next step. If A/C compressor clutch does not engage, see A/C CLUTCH CIRCUIT DIAGNOSIS.
3. Check For Cooling Fan If vehicle is equipped with electric cooling fan, go to next step. If vehicle is not equipped with electric cooling fan, go to step 5).
4. Check Operation Of Cooling Fan If electric cooling fan runs when A/C compressor clutch is engaged, go to next step. If electric cooling fan does not run when compressor clutch is engaged, see ENGINE COOLING FANS article in the ENGINE COOLING section.
5. Component Checks Check for loose, missing or damaged compressor drive belt. Check for loose or disconnected A/C clutch, cyclic switch (except Tempo and Topaz) or clutch cycling pressure switch (Tempo and Topaz) wires and connectors. Check for damaged A/C compressor clutch. Check for blown fuses and disconnected blower motor resistor. Check for proper operation of blower motor, vacuum motors and doors. Check for loose vacuum lines or misadjusted control cables (if equipped). Ensure A/C-heater control panel electrical and vacuum connections are secure. If any item is not functioning properly, repair item as necessary and go to next step. If all items are functioning properly, go to step 7).
6. Check System If system now operates properly, fault conditions were corrected, go to step 1). If system still does not operate properly, go to next step.
7. Check A/C Compressor Clutch Connect manifold gauge set. Perform A/C SYSTEM PERFORMANCE test. See appropriate A/C-HEATER SYSTEM - MANUAL article (for Crown Victoria) and A/C-HEATER SYSTEM - MANUAL article (for Grand Marquis) in the AIR CONDITIONING & HEAT section. If A/C compressor clutch cycles properly and system pressure is within limits, A/C system is operating properly. If compressor cycles very rapidly (5 seconds on, 5 seconds off) and suction pressure is within limits, go to step 8). If compressor runs continuously, go to step 9). If compressor cycles on above 52 psi (3.7 kg/cm 2 ) and off below 20 psi (1.4 kg/cm 2 ), replace A/C low pressure cut-off switch (except Tempo and Topaz) or clutch cycling pressure switch (Tempo and Topaz). After replacing switch, verify A/C system operation. If system still is not operating properly, reinstall original switch and go to step 8). NOTE: It is not necessary to discharge A/C system when replacing clutch cycling or A/C low pressure cut-off switches.
8. Check System Check system for refrigerant leaks. If leaks exist in A/C system, repair leaks as necessary. Evacuate, recharge and verify A/C system operation. If leak does not exist in A/C system, check for a restricted orifice tube or liquid line. Also check for moisture or low refrigerant charge. Repair A/C system as necessary and verify A/C system operation. NOTE: A compressor running continuously is normal operation, when there is high humidity and ambient temperature is greater than 80°F (27°C).
9. Check Clutch Cycling Switch Disconnect blower motor connector. Check low pressure gauge for pressure at which A/C compressor clutch cycles off. If clutch cycles off between 22-25 psi (1.5-1.8 kg/cm 2 ) and ambient temperature is more than 80°F (27°C), A/C system is operating properly. If clutch cycles off between 22-25 psi (1.5-1.8 kg/cm 2 ) and ambient temperature is less than 80°F (27°C), discharge refrigerant from A/C system. Evacuate, recharge and verify A/C system pressures. If clutch cycles off below 22 psi (1.5 kg/cm 2 ), replace A/C low pressure cut-off switch or clutch cycling pressure switch. After replacing switch, verify A/C system operation.

BLOWER MOTOR RUNS IN HIGH SPEED IN ALL SWITCH POSITIONS

1. Check Voltage At Blower Motor Speed Control Module Start engine. Set A/C system to MAX A/C and blower motor switch to medium speed position. If blower motor remains in high speed, turn engine off and disconnect blower motor speed control connector. Start engine, set A/C system to MAX A/C and blower motor switch to low speed. Measure voltage between blower motor speed control module connector terminals No. 2 (Light Green/White wire) and No. 5 (Light Blue/Orange wire). Move blower motor speed control switch through all speed settings. In HI blower position, zero volts should be present. In all other positions, 1-2 volts should be present. If voltage is as specified, go to step 4). If voltage is not as specified, go to next step.
2. Measure Voltage If voltage measured in step 1) is greater than 2 volts in all switch positions, replace blower motor speed control module. If voltage measured in step 1) is less than 2 volts in all switch positions, go to next step.
3. Check For Zero Voltage If voltage measured in step 1) is zero for all switch positions, go to step 5). If voltage measured in step 1) is not zero for all switch positions, go to step 1) and retest.
4. Check Voltage Measure voltage between blower motor speed control module connector terminals No. 3 (Yellow/Red wire) and No. 5 (Light Blue/Orange wire). Move blower motor speed control switch through all speed positions, except HI position. If zero volts is present, replace blower motor speed control module. If more than zero volts is present, replace Automatic Temperature Control (ATC) module. After repairs, verify A/C system operation.
5. Check Voltage Connect blower motor speed control module connector. Start engine, set A/C system to MAX A/C, and heater blower motor switch to medium speed position. Measure voltage at ATC control module connector terminal No. 6 (Yellow/Red wire). If 1-2 volts is not present, go to next step. If 1-2 volts is present, repair Yellow/Red wire circuit between ATC module and blower motor speed control module.
6. Check Voltage At Control Module If zero volts is measured in step 5), replace ATC module. If zero volts is not measured in step 5), go to step 1) and retest. After repairs, verify A/C system operation.

BLOWER MOTOR DOES NOT RUN IN LOW OR MEDIUM SPEED

1. Check Voltage Start engine, set A/C system to MAX A/C, and blower motor switch to LO or medium speed position. If blower motor does not come on, turn ignition off. Disconnect blower motor speed control connector. Start engine, set A/C system to MAX A/C, and blower motor switch to LO position. Measure voltage between blower motor speed control connector terminals No. 2 (Light Green/White wire) and No. 5 (Light Blue/Orange wire). If 1-2 volts is not present, go to next step. If 1-2 volts is present, replace blower motor speed control module. After repairs, verify A/C system operation.
2. Check Voltage At Terminals No. 2 & 5 If voltage measured in step 1) is greater than zero volts at LO switch position, go to next step. If zero volts is not present, go to step 1) and retest.
3. Check Voltage Connect blower motor speed control connector. Start engine, set A/C system to MAX A/C, and blower motor switch to LO position. Measure voltage between ground and Automatic Temperature Control (ATC) module connector terminal No. 6 (Yellow/Red wire). If voltage is not 1-2 volts, go to next step. If voltage is 1-2 volts, repair Yellow/Red wire circuit between ATC module and blower motor speed control module. After repairs, verify A/C system operation.
4. Check Voltage At Terminal No. 6 If voltage measured in step 3) is zero volts, replace ATC module. If voltage measured is not zero volts, go to step 3) and retest. After repairs, verify A/C system operation.

BLOWER MOTOR DOES NOT RUN IN HIGH SPEED

1. Voltage Check Start engine. Set A/C system to MAX A/C, and turn blower motor switch to LO or medium speed. After blower motor comes on, turn switch to HI position. If blower motor does not go to full high speed, turn ignition off. Disconnect blower motor speed control connector. Start engine, set A/C system to MAX A/C, and blower motor switch to HI position. Measure voltage between blower motor speed control connector terminals No. 3 (Yellow/Red wire) and No. 5 (Light Blue/Orange wire). If less than 10 volts is present, go to next step. If 10 volts or more is present, replace blower motor speed control.
2. Measure Voltage Connect blower motor speed control connector. Start engine. Set system to MAX A/C and blower motor switch to HI position. Measure voltage between ground and ATC module connector terminal No. 5 (Light Green/White wire). Turn blower motor switch to HI position. If voltage is less than 10 volts, replace ATC module. If 10 volts or more is present, repair Light Green/White wire circuit between ATC module and blower motor speed control module. After repairs, verify A/C system operation.

A/C CLUTCH CIRCUIT DIAGNOSIS

1. Check System Operation Ensure ambient temperature of working area is greater than 50°F (10°C). Start engine and set A/C system to MAX A/C. Ensure battery voltage is greater than 12.5 volts. Place blower switch in HI position. If compressor clutch engages after 5-second delay, circuit is operating properly. If clutch does not engage after 5-second delay, go to next step.
2. A/C Low Pressure Cut-Off Switch Turn engine off. Disconnect electrical connector from A/C low pressure cut-off switch (on suction hose). Start engine and set A/C system to MAX A/C. Connect jumper wire across switch harness connector terminals. If clutch engages, go to next step. If clutch does not engage, go to step 4).
3. Check Refrigerant Pressure Turn engine off. Connect manifold gauge set and note pressure readings. If pressure reading is less than 50 psi (3.5 kg/cm 2 ), check system for leaks and repair as necessary. If pressure reading is greater than 50 psi (3.5 kg/cm 2 ), replace A/C low pressure cut-off switch. After repairs, verify A/C system operation.
4. Check Voltage At A/C Low Pressure Cut-Off Switch With engine running, measure voltage between ground and low pressure cut-off switch connector Purple wire terminal. Measure voltage between ground and A/C high pressure cut-off switch connector Pink/Light Blue wire terminal. If battery voltage is not present, go to next step. If battery voltage is present, go to step 8).
5. Check A/C Control Switch Turn engine off and ignition switch to RUN position. Set A/C system to MAX A/C. Check for battery voltage at A/C control switch Purple wire terminal. If battery voltage does not exist, go to next step. If battery voltage exists, repair open Purple wire between A/C control switch and A/C low pressure cut-off switch. After repairs, verify A/C system operation.
6. Check Power Supply To A/C Control Switch Turn engine off and ignition switch to RUN position. Check for battery voltage at A/C control switch connector White/Light Blue wire terminal. If battery voltage exists, replace A/C control switch. If battery voltage does not exist, go to next step.
7. Check Power Supply To A/C Control Panel Turn engine off and ignition switch to RUN position. Measure voltage at fuse panel connector White/Light Blue wire terminal. If battery voltage is not present, check fuse No. 10 (15-amp) and/or repair White/Light Blue wire between A/C control switch and fuse block. If fuse is blown, check for short in A/C clutch diode circuit. If battery voltage is present, go to step 8). NOTE: If less than 10 volts is present at terminal, check charging system output and/or check for high resistance in White/Light Blue wire. Repair wire as necessary. After repairs, verify A/C system operation.
8. Check Clutch Circuits Turn ignition to RUN position. Measure voltage across clutch coil harness connector terminals. If 10 volts or more is present, go to step 10). If less than 10 volts is present, go to next step.
9. Check Clutch Voltage Turn ignition switch to RUN position. Measure voltage between ground and clutch coil harness connector Black/Yellow wire terminal. If less than 10 volts is present, go to step 13). If 10 volts or more is present, go to step 12).
10. Check Clutch Coil Turn ignition off. Disconnect clutch coil connector. Using jumper wire, connect one clutch coil connector terminal to battery voltage. Using another jumper wire, connect other clutch coil terminal to ground. If clutch does not engage, go to next step. If clutch engages, clean clutch coil connector terminals and retest system.
11. Check Clutch Air Gap Using feeler gauge, check air gap between pulley and hub. Air gap should be .014-.033" (.35-.84 mm). If air gap is not within specification, reset gap and go back to step 10). If air gap is within specification, replace clutch coil. After repairs, verify A/C system operation.
12. Check Clutch Ground Check continuity of Black wire from clutch coil connector to ground. If continuity is present, check ground connection and clean as necessary. If continuity does not exist, repair Black wire as necessary and retest system. After repairs, verify A/C system operation.
13. Check Voltage At A/C Cut-Out Relay Turn ignition on. Check for voltage between A/C low pressure cut-off switch connector Pink/Light Blue wire terminal and A/C cut-out relay connector terminal No. 30 (Dark Green/Orange wire). If voltage is present, go to next step. If voltage is not present, check continuity across A/C high pressure cut-out switch. If A/C high pressure cut-out switch is okay, repair open circuit between A/C low pressure cut-off switch and A/C cut-out relay. After repairs, verify A/C system operation.
14. Check A/C Cut-Out Relay Turn ignition off. Disconnect A/C cut-out relay connector. Start engine and turn A/C system on. Connect jumper wire across cut-out relay connector terminal No. 30 (Dark Green/Orange wire) and cut-out relay connector terminal No. 87A (Black/Yellow wire). If compressor clutch engages, remove jumper wire and go to next step. If clutch does not engage, check for shorted diode or Black/Yellow wire. Repair wire and/or replace diode as necessary. After repairs, verify A/C system operation.
15. Check A/C Cut-Out Relay Operation Start engine and turn A/C system on. Reconnect cut-out relay connector, and note if cut-out relay energizes and A/C compressor clutch circuit opens. If cut-out relay does not energize, replace cut-out relay and verify A/C system operation. If cut-out relay energizes, Powertrain Control Module (PCM) is interrupting compressor clutch circuit. For PCM diagnostic procedures, see appropriate ENGINE PERFORMANCE article.

Preliminary Procedures

1. Warm engine to normal operating temperature. Ensure refrigerant system is fully charged, compressor belt is correctly tightened and condenser airflow is not restricted.
2. Ensure vehicle interior temperature is 70-80°F (21-27°C). Check air distribution for proper operation in each function. See CONTROL PANEL SETTINGS under OPERATION. If a fault is found here, correct it before going to TEMPERATURE CONTROL INCORRECT.

System Functional Test

1. Engine speed should be at least 1200 RPM. Set function selector lever to VENT position. Check blower operation in LO and HI settings. If blower operation is okay, move selector blower lever to AUTO position. If blower motor does not operate in all positions, correct fault. See BLOWER MOTOR DIAGNOSIS under TESTING.
2. Move temperature control lever from 65 to 85 and observe blower motor speed change and air temperature change. Move temperature control lever back to 65 and observe blower and temperature outputs. See INTERIOR TEMPERATURE PERFORMANCE TEST table.
3. Place temperature control lever at 65. Move function lever to NORM A/C position. Outside/recirculated air door should open, and A/C compressor clutch should engage to produce colder air temperatures.
4. Move temperature control lever to 75. Blower motor speed should slow to low or medium speed, and discharge air temperature should rise to a moderate level.

INTERIOR TEMPERATURE PERFORMANCE TEST

Preliminary Procedure

Warm engine to normal operating temperature. Ensure vehicle interior temperature is 70-80°F (21-27°C). Engine speed should be at least 1200 RPM. After determining symptoms and suspect component(s), test appropriate component or system. See TESTING.

Insufficient Or No Heat

Check for hot heater hoses to and from heater core. Also ensure blend door is in full heat position.

Insufficient Or No Cooling

Check A/C refrigerant and outside/recirculated air door vacuum circuit.

Alternating Long Periods Of Hot & Cool Air

Aspirator hose is blocked or disconnected. Sensor assembly is not sampling interior air.

Sensor Assembly Buzzes

Sensor assembly output line is blocked or pinched.

Heating & Cooling Okay, But Temp Settles Too Cool Or Too Warm

Sensor assembly is out of adjustment or malfunctioning, or seals are leaking. Control module is defective.

Temperature Rises During Acceleration

Observe distribution door vacuum motor while engine is under load. If vacuum drops, an inoperative check valve or vacuum leak exists. A serious leak causes air distribution to shift to defrost position.

Compressor Clutch Does Not Engage

Check for low refrigerant charge, open circuit to compressor clutch coil, faulty clutch cycling pressure switch and faulty compressor cut-out relay.

TESTING

A/C SYSTEM PERFORMANCE

Note. Perform A/C system performance test when reasonably certain that A/C system (compressor, etc.) is okay and interior temperature is 70-80°F (21-27°C).

1. Blower Motor Operation Ensure interior temperature is 70-80°F (21-27°C). Ensure blower motor leads are connected and A/C 3 fuses in instrument panel fuse box are good. Verify battery voltage exists at control module terminal No. 10 (Light Green/Yellow wire). Verify battery voltage from A/C damper door switch exists at control module terminal No. 11 (Orange wire). If blower motor operates, go to next step. If blower motor does not operate, see TROUBLE SHOOTING section.
2. Blower Function Ensure A/C blower motor and blower motor controller connections are clean and tight. If blower motor operates in AUTO, or from LOW to HIGH, go to next step. If blower motor does not operate in AUTO, or from LOW to HIGH, see TROUBLE SHOOTING section.
3. Air Discharge Locations Check for incorrect or erratic air discharge locations. If air discharge operates correctly, go to next step. If air discharge locations are erratic or incorrect, check for leaking or disconnected vacuum lines. Check for leaking, damaged or inoperative vacuum motors and/or valves. Repair or replace as necessary.
4. A/C Blower Motor Speed Operate system. Select different blower speeds. Verify wiring continuity in Yellow/Red wire, Light Green/White wire and Light Blue/Orange wire between blower motor speed controller connector and control module connector. If blower motor speed varies according to switch position, go to next step. If blower motor stays in high speed in all switch positions, see TROUBLE SHOOTING section.
5. Discharge Air Temperature Operate system. Set blower motor switch in AUTO position. If discharge air temperature varies with change in temperature lever position, go to next step. If discharge air temperature does not vary, check connections at blend door actuator. Ensure continuity exists in White/Yellow wire between electronic door actuator motor and control module connector. Ensure continuity exists in Purple wire between electronic door actuator motor and control module connector. Repair wire(s) as necessary.
6. A/C Blower Motor Speed Operate system. Change temperature lever positions. If blower motor speed changes with temperature lever position, go to next step. If blower speed does not change with temperature lever position, see BLEND DOOR ACTUATOR.
7. Discharge Air Temperature Hot Operate system with blower switch in AUTO. If discharge air temperature does not remain at full heat when temperature lever position is changed, go to next step. If discharge air temperature remains at full heat at all temperature lever positions, ensure automatic temperature control sensor connector and hose are connected. Ensure continuity exists in White/Orange wire between automatic temperature control sensor and control module connector. Ensure continuity exists in Pink/Black wire between automatic temperature control sensor and control module connector. Repair wire(s) as necessary.
8. Blower Motor Speed Set blower motor control to maximum speed. If blower motor does not operate at maximum speed, go to next step. If blower operates at maximum speed, ensure ambient air temperature sensor connection is clean and tight. Ensure continuity exists in Light Blue/Orange wire between ambient air temperature sensor and control module connector. Ensure continuity exists in Pink/Black wire between ambient air temperature sensor and control module connector. Repair wire(s) as necessary.
9. Operate System With Blower Switch In AUTO Position Verify blower motor speed remains unchanged when temperature control lever is moved slowly from 65 to 85°F. Ensure discharge air temperature changes. If discharge air temperature does not change when temperature control lever is moved, go to next step. If discharge temperature changes, ensure automatic air control temperature sensor connection is clean and tight. Ensure continuity exists in White/Orange wire between automatic air temperature control sensor and control module connector. Ensure continuity exists in Pink/Black wire between automatic air temperature control sensor and control module connector. Repair wire(s) as necessary.
10. Set Temperature Selector Lever 72-78°F (22-26°C) If blower motor speed does not oscillate rapidly or change constantly, go to next step. If blower motor speed oscillates rapidly or changes constantly, ensure ambient air temperature sensor connection is clean and tight. Ensure continuity exists in Light Blue/Orange wire between ambient air temperature sensor connector and control module connector. Repair wire as necessary.
11. Change Blower Motor Speed Setting If blower motor speed changes, go to next step. If blower motor speed does not change, see TROUBLE SHOOTING section.
12. System Operation Change blower motor speed setting. If system operates correctly and reaches maximum heating or cooling, go to next step. If system does not operate properly, check Yellow/White wire and Light Green/Yellow wire at control module connector for loose or corroded connections. Repair connections as necessary. Disconnect negative battery cable for 2 minutes to allow system to recalibrate. Retest system.
13. Function Selection Operation Ensure engine coolant temperature is greater than 120°F (49°C). Set function lever to FLOOR position. If there is air output at floor position, go to next step. If there is no air output at floor position, ensure engine coolant level is correct. Check Light Blue/Orange wire between control module and temperature control lock-out valve and switch for continuity. Repair wire as necessary.
14. Temperature Control Lock-Out Valve & Switch Operation Ensure engine coolant temperature is greater than 120°F (49°C). Set function lever to FLOOR position. If there is no air output at floor position at any time, go to next step. If there is air output at floor position at all times, see TROUBLE SHOOTING section.
15. Blower Motor Operation Set blower motor switch to OFF position. If blower motor stops operating, go to next step. If blower motor continues to operate, check Orange/Black wire between blower motor speed controller connector and blower motor connector for short circuit to battery voltage. Repair wire as necessary. If wire is good, check blend door actuator for damage. Replace actuator if necessary.
16. System Temperature Operation Operate system. If system alternates between long periods of heating and cooling, ensure automatic temperature control sensor hose and elbow are connected in dash. Ensure hose and elbow are free of blockages and kinks. Repair hose and elbow as necessary. If system does not alternate between long periods of heating and cooling, functional testing is completed.

AIRFLOW & VACUUM LEAK TESTS

1. Check in-line and multiple vacuum connectors for proper installation. Listen for hissing sound. Move function lever to determine which selector valve positions are leaking.
2. Determine which color vacuum lines are responsible for function indicated when vacuum leak occurs. Individually pinch off suspect lines near vacuum motor. If hiss stops, repair vacuum lines as necessary.
3. If hiss does not stop, ensure vacuum motor holds vacuum. If motor will not hold vacuum, replace vacuum motor. Individually pinch off suspect lines near control assembly or suspect line connector. If hiss stops, repair vacuum lines as necessary. If hiss does not stop, replace function selector valve.
4. Move temperature control lever from 65-85°F (18-29°C). If hiss stops at some settings, check function associated with setting. If hiss-ing does not stop, check vacuum source line (Black) from vacuum reservoir to vacuum selector valve for damage.
5. If vacuum source line is okay, pinch vacuum source line at vacuum selector valve. If hiss stops, replace vacuum selector valve. If hiss does not stop, pinch vacuum source line (Black) off at temperature control lock-out switch. If hiss stops, replace thermal blower lock-out switch.
6. If hiss does not stop, check vacuum tank, check valve, vacuum source line and connectors. Repair or replace as necessary.

1. Disconnect electrical connector from rear of ATC control module. Turn ignition switch to RUN position. Using jumper wires, connect positive (+) lead to terminal No. 4 (White/Light Green wire). Connect negative (-) lead to terminal No. 3 (Gray/Red wire). Ensure actuator moves to maximum cooling position.
2. Reversing leads should drive actuator to maximum heating position. If actuator does not move in both directions, replace actuator.
3. If actuator moves okay in both directions, leave jumper wires connected for maximum heating position, and energize actuator to maximum heating position for 15-20 seconds.
4. Using ohmmeter, check resistance between control module connector terminals No. 7 (Yellow/Light Green wire) and No. 13 (Black/White wire). Resistance should be 4500-6000 ohms. If resistance is not as specified, replace actuator.
5. Check resistance between control module connector terminals No. 14 (Dark Green/Orange wire) and No. 13 (Black/White wire). Resistance should be 250-1500 ohms. If resistance is not as specified, replace actuator.
6. Check resistance between control module connector terminals No. 14 (Dark Green/Orange wire) and No. 7 (Yellow/Light Green wire). See WIRING DIAGRAM. Resistance should be 3500-6000 ohms. If resistance is not as specified, replace actuator.
7. If resistance and actuator function are correct, damage to wiring harness or failure of ATC control module has caused actuator failure. Disconnect actuator connector and ATC control module connector.
8. Using ohmmeter, check continuity in wiring harness according to BLEND DOOR ACTUATOR WIRING CONTINUITY table. See WIRING DIAGRAM for terminal identification. Repair harness as necessary. If wiring harness is okay, replace ATC control module.

BLEND DOOR ACTUATOR WIRING CONTINUITY

BLOWER MOTOR DIAGNOSIS

Note. Blower motor circuit is grounded behind right kick panel.

Blower Motor Current Draw

Blower motor power is supplied through a 30-amp fuse in passenger compartment fuse panel. Check motor current draw. See BLOWER MOTOR CURRENT DRAW SPECIFICATIONS table.

BLOWER MOTOR CURRENT DRAW SPECIFICATIONS (1)

No Blower Operation

Check for disconnected blower motor leads at blower motor. Check for blown 30-amp fuse in blower motor circuit, defective motor and open control panel connector. Blower motor speed controller and high blower relay may be defective. Repair or replace as necessary.

No Blower In FLOOR Mode

Ensure engine temperature is more than 110°F (43°C). Check for open circuit in thermal blower lock-out switch at control panel on right side of instrument panel. Check for open circuit in blower switch. Check for low coolant level. Repair or replace as necessary.

Blower Will Not Turn Off

Check for inoperative selector switch on control panel and short circuit to battery voltage in wiring harness. Repair or replace as necessary.

Blower Always On In FLOOR Mode; No Cold Engine Lock-Out

Ensure engine temperature is less than 110°F (43°C) in order for cold engine lock-out to work. Check for inoperative thermal blower lock-out switch and short in wiring. Repair or replace as necessary.

TEMPERATURE CONTROL LOCK-OUT SWITCH

Test procedure is not available from manufacturer.

BLOWER MOTOR SPEED CONTROLLER

Test procedure is not available from manufacturer.

REMOVAL & INSTALLATION

Note. For replacement of components not covered in this article, see A/C-HEATER SYSTEM - MANUAL article (for Crown Victoria) and A/C-HEATER SYSTEM - MANUAL article (for Grand Marquis) in the AIR CONDITIONING & HEAT section.

1. Working in engine compartment, disconnect blower motor lead from wiring harness connector. Remove blower motor cooling tube from blower motor. Remove 4 blower mounting plate screws.
2. Turn motor and wheel assembly slightly right so bottom edge of mounting plate follows contour of wheelwell splash panel. While still in blower housing, lift motor and fan assembly upward from housing. To install, reverse removal procedure.

1. Disconnect negative battery cable. Remove right and left instrument panel moldings. Remove cluster finish panel screws.
2. Remove headlight automatic dim switch knob. Remove headlight switch shaft. Remove steering column retaining bolts, and lower steering column. Remove PRNDL cable from gear selector. Lower steering column so it rests on front seat. Remove instrument cluster finish panel. Remove center finish panel.
3. Remove 4 screws from control panel and pull away from dash. (Scheme 1) Unplug electrical connections and vacuum connector from control panel assembly.
4. Automatic temperature control sensor is mounted behind instrument panel. (Scheme 3) To remove sensor, remove mounting screws. Unplug electrical connector, and remove sensor. To install, reverse removal procedure.

1. Disconnect negative battery cable. Discharge A/C system using approved refrigerant recovery/recycling equipment. Disconnect lines at accumulator-drier and evaporator using Spring-Lock Couplers (T81P-19623-G1 and T81P-19623-G2). Position hoses away from evaporator case, and cap all openings.
2. Disconnect 2-wire plug from cycling clutch pressure switch on accumulator-drier. (Scheme 8) Drain coolant from radiator. Disconnect heater hoses from heater core, and plug core openings.
3. Turn wheels left to access wheelwell splash panel support bracket. Remove screw and splash panel support bracket from back portion of wheelwell.
4. Remove 6 screws from right hood seal bracket assembly. Remove copper hood ground clip from underneath hood seal. Remove hood seal assembly from right side of vehicle.
5. Set aside all vacuum hoses and wiring which pass over top of evaporator case assembly. Disconnect blower motor wiring and 2 large wiring harnesses crossing evaporator assembly, and position aside.
6. Fold back carpet on passenger side, and remove bottom left screw of 2 screws supporting inlet recirculating air assembly. Disconnect in-car temperature sensor air tube from evaporator air tube port.
7. From under hood, remove nuts from evaporator assembly mounting studs and 2 screws from blower motor assembly. Pull evaporator assembly off 2 bottom studs and then off top stud. Maneuver case up and over wheelwell splash panel. To install, reverse removal procedure. Recharge A/C system. Refill and bleed cooling system.

Scheme 8

EVAPORATOR CORE

Note. Replace accumulator-drier whenever evaporator core is replaced.

1. Remove evaporator case. See EVAPORATOR CASE. Remove firewall seal. Remove heat shield from bottom of evaporator case. Remove 6 screws holding case halves together. Separate case halves.
2. Disconnect accumulator-drier inlet from evaporator core outlet tube. Remove accumulator-drier and evaporator core mounting bracket screws. Remove evaporator core. (Scheme 9)
3. To install, reverse removal procedure. Add 3 ounces of clean refrigerant oil to evaporator core and use new "O" rings. Using Caulking Cord (D9AZ-19560-A), seal evaporator case along case flange and around evaporator core tubes.

Scheme 9

1. Disconnect negative battery cable. Drain coolant from radiator. Disconnect heater hoses from heater core, and plug core openings.
2. Remove 3 nuts, located below windshield wiper motor, attaching left end of plenum to firewall. Remove nut retaining upper left corner of evaporator case to firewall.
3. Disconnect vacuum supply hose from vacuum source. Remove vacuum harness from thermal blower lock-out switch. Push grommet and vacuum supply hose into passenger compartment. Remove left and right lower instrument panel insulators. Remove glove box.
4. Remove instrument panel mounting screws. Pull instrument panel back as far as possible without disconnecting wiring harness. Remove right kick panel. Remove cross body bracket. Disconnect temperature blend door actuator.
5. Disconnect air duct from evaporator case connector. Label and disconnect all vacuum harnesses. Remove 2 screws attaching passenger side of floor air distribution duct to plenum. (Scheme 10) Remove 2 lower panel door vacuum motor-to-mounting bracket screws to access right screw (if necessary).
6. Remove plastic push fastener holding floor air distribution duct to left end of plenum. Remove floor air distribution duct. Remove 2 nuts from studs along lower edge of plenum. Remove plenum assembly from vehicle.
7. Remove 4 heater core cover screws and cover. (Scheme 8) Remove core and seal from plenum. To install, reverse removal procedure.

Scheme 10

Note. Temperature control lock-out valve and switch may also be referred to as Thermal Blower Lock-Out (TBLO) switch.

1. Disconnect negative battery cable. Disconnect vacuum harness and wiring harness from TBLO. Loosen clamps at TBLO. Remove switch from heater hose.
2. To install, reverse removal procedure. When installing TBLO, tighten clamps to 16-21 INCH lbs. (2-2.4 N.m).

Unplug blower motor speed controller connector. (Scheme 6) Remove 2 controller mounting screws from evaporator case, and lift out controller. To install, reverse removal procedure.

Automatic A/C-Heater System Wiring Diagram. Scheme 11