E: Magnetic A/C Clutch Circuit Diagnosis

E1 CHECK SYSTEM OPERATION

NOTE: The ambient temperature must be above approximately 10°C (50°F) for A/C compressor operation.

- Start engine.

- Turn A/C on.

- Check battery voltage (if not 12.5 V or more, refer to charging system diagnosis).

- Turn blower motor switch to HI.

- Does A/C clutch engage after 5 second delay?

- Yes
Circuit functioning properly.

- No
Go to E2.

E2 A/C CYCLING SWITCH

- Disconnect electrical connector from A/C cycling switch.

- Jumper harness pins.

- Engine must be running with A/C on.

- Does A/C clutch engage?

- Yes
Go to E3.

- No
Go to E4.

E3 CHECK REFRIGERANT SYSTEM PRESSURE

- Connect gauge set to service ports and observe pressure.

- Reading should be above 344.75 kPa (50 psi) with the engine off.

- Is pressure above 344.75 kPa (50 psi)?

- Yes
Replace A/C cycling switch.

- No
Check refrigerant system for leaks. Service system as required. Go to E1.

E4 CHECK VOLTAGE AT A/C CYCLING SWITCH

- Check for battery positive voltage (B+) at the A/C cycling switch electrical connector Circuit 348 (P) (Crown Victoria/Grand Marquis), Circuit 883 (PK/LB) (Town Car) to ground

- Check for B+ at A/C high pressure cutout switch electrical connector Circuit 883 (PK/LB) (Crown Victoria/Grand Marquis), Circuit 441 (R/Y) (Town Car) to ground.

- Is there B+?

- Yes
Go to E7.

- No
Go to E5.

E5 CHECK A/C CONTROL ASSEMBLY

- Check for B+ at A/C control assembly Circuit 348 (P) (Crown Victoria/Grand Marquis), Circuit 883 (PK/LB) (Town Car) to ground.

- Is there B+?

- Yes
Service wiring as necessary. Go to E1.

- No
Go to E6.

E6 CHECK A/C CONTROL SUPPLY VOLTAGE

- Check for B+ at A/C control assembly Circuit 294 (W/LB) (Crown Victoria/Grand Marquis), Circuit 298 (P/O) (Town Car) to ground.

- Ignition switch must be in the RUN position.

- Is there B+?

- Yes
Replace A/C control assembly. Go to E1.

- No
Service wiring for opens or shorts. Check fuse, if blown, check clutch diode for short. Service as necessary. Go to E1.

E7 CHECK A/C CLUTCH CIRCUITS

- Check for voltage across harness connector at A/C clutch field coil.

- A minimum of 10 volts is required.

- Is there a minimum of 10 volts?

- Yes
Go to E9.

- No
Go to E8.

E8 CHECK A/C CLUTCH VOLTAGE

- Check for voltage at A/C clutch harness Circuit 347 (BK/Y) (Crown Victoria/Grand Marquis), Circuit 348 (P) (Town Car) and ground.

- Is there a minimum of 10 volts?

- Yes
Go to E11.

- No
Go to E12.

E9 JUMP A/C CLUTCH FIELD COIL

- Disconnect A/C clutch field coil and jump B+ and ground to A/C clutch field coil.

- Does A/C clutch engage?

- Yes
Clean coil electrical terminals and retest system.

- No
Go to E10.

E10 CHECK A/C CLUTCH AIR GAP

- Check air gap between A/C clutch and A/C clutch pulley. Air gap must be within specified limits. Refer to Heating and Air conditioning/Compressor HVAC/Specifications. Specifications

- Is air gap within specifications?

- Yes
Replace A/C clutch field coil.

- No
Reset air gap. GO to E9.

E11 CHECK A/C CLUTCH GROUND

- Check Circuit 57 (BK) at clutch harness connector for continuity to ground. Must have continuity with minimum resistance.

- Is there continuity?

- Yes
Check ground connection. Clean as necessary. Go to E1.

- No
Service Circuit and/or ground connection.

E12 CHECK VOLTAGE AT A/C CUTOUT RELAY

- Check for B+ at the A/C cutout relay Circuit 198 (DG/O) (Crown Victoria/Grand Marquis), 347 (BK/Y) (Town Car) to ground.

- Is there voltage?

- Yes
Go to E14.

- No
Go to E13.

E13 CHECK VOLTAGE AT A/C PRESSURE CUT-OFF SWITCH

- Check for B+ at the A/C pressure cut-off switch Circuit 198 (DG/O) (Crown Victoria/Grand Marquis), 347 (BK/Y) (Town Car) to ground.

- Is there voltage?

- Yes
Service Circuit 198 (DG/O) or 347 (BK/Y). Go to E1.

- No
Replace A/C pressure cut-off switch. Go to E1.

E14 CHECK A/C CUTOUT RELAY

- Disconnect connector from relay.

- Jumper across the connector Circuit 198 (DG/O) (Crown Victoria/Grand Marquis), Circuit 347 (BK/Y) (Town Car) to 347 (BK/Y) (Crown Victoria, Grand Marquis), 348 (P) (Town Car).

- With engine running and A/C on, check for A/C clutch engagement.

- Does A/C clutch engage?

- Yes
Go to E15.

- No
Check for shorted diode or open Circuit 347 (BK/Y) (Crown Victoria/Grand Marquis), 348 (P) (Town Car).

E15 CHECK A/C CUTOUT RELAY OPERATION

- With the engine running, reconnect the harness connector to the A/C cutout relay and check to see if relay energizes. The A/C clutch circuit will open if the relay energizes.

- Does relay energize?

- Yes
The powertrain control module (PCM) is causing relay to energize and interrupt A/C compressor circuit. Any of the following can be the cause.

- Throttle position sensor (TP sensor) sending wide open throttle signal to powertrain control module. Disconnect electrical connector to remove throttle position sensor from circuit. A/C clutch will engage if throttle position sensor is sending wide open throttle cutout signal.

- Engine coolant temperature sensor (ECT sensor) sending hot coolant signal to powertrain control module. Disconnect electrical connector from engine coolant temperature sensor.

- A/C clutch will engage if engine coolant temperature sensor is sending hot coolant signal to the powertrain control module. A/C ON circuit to powertrain control module open. If circuit is open, powertrain control module will not receive signal from A/C pressure cut-off switch to turn A/C clutch on.

- No
Replace A/C cutout relay.