Compressor clutch coil. Electronic cycling clutch switch (front unit only)

Compressor clutch coil

RELAY TEST

The compressor clutch relay (Fig. 8) is located in the Power Distribution Center (PDC). Refer to the PDC label for relay identification and location.

Remove the relay from the PDC to perform the following tests: (1) A relay in the de-energized position should have continuity between terminals 87A and 30, and no continuity between terminals 87 and 30. If OK, go to Step 2. If not OK, replace the faulty relay.

(2) Resistance between terminals 85 and 86 (electromagnet) should be 75 +- 5 ohms. If OK, go to Step 3. If not OK, replace the faulty relay.

(3) Connect a battery to terminals 85 and 86.

There should now be continuity between terminals 30 and 87, and no continuity between terminals 87A and 30. If OK, see Relay Circuit Test in the Diagnosis and Testing section of this group. If not OK, replace the faulty relay.

RELAY CIRCUIT TEST

For circuit descriptions and diagrams, refer to 8W-42 - Air Conditioning/Heater in Group 8W - Wiring Diagrams.

(1) The relay common feed terminal cavity (30) is connected to fused battery feed. There should be bat-tery voltage at the cavity for relay terminal 30 at all times. If OK, go to Step 2. If not OK, repair the open circuit to the fuse in the PDC as required.

(2) The relay normally closed terminal (87A) is not used in this application. Go to Step 3.

(3) The relay normally open terminal cavity (87) is connected to the compressor clutch coil. There should be continuity between this cavity and the A/C compressor clutch relay output circuit cavity of the compressor clutch coil wire harness connector. If OK, go to Step 4. If not OK, repair the open circuit as required.

(4) The relay coil battery terminal (86) is connected to the fused ignition switch output (run/start) circuit. There should be battery voltage at the cavity for relay terminal 86 with the ignition switch in the On position. If OK, go to Step 5. If not OK, repair the open circuit to the fuse in the junction block as required.

(5) The coil ground terminal cavity (85) is switched to ground through the Powertrain Control Module (PCM). There should be continuity between this cavity and the A/C compressor clutch relay control circuit cavity of the PCM wire harness connector C (gray) at all times. If not OK, repair the open circuit as required.

Fig. 8 Compressor Clutch Relay

Electronic cycling clutch switch (front unit only)

For circuit descriptions and diagrams, refer to 8W-42 - Air Conditioning/Heater in Group 8W - Wiring Diagrams. Use a volt/ohmmeter to test the electronic cycling clutch switch. Verify that the refrigerant system has the correct refrigerant charge.

Check that both the low and high pressure cut-off switches are functional as described in the Diagnosis and Testing section of this group before testing the electronic cycling clutch switch.

(1) Disconnect and isolate the battery negative cable. Unplug the wire harness connectors at the electronic cycling clutch switch and the high pressure cut-off switch. Check for continuity between the C90A circuit cavities in the body half of the electronic cycling clutch switch wire harness connector and the high pressure cut-off switch wire harness connector.

There should be continuity. If OK, go to Step 2. If not OK, repair the open circuit as required.

(2) Unplug the wire harness connector at the low pressure cut-off switch. Check for continuity between the C2 circuit cavities in the body half of the electronic cycling clutch switch wire harness connector and the low pressure cut-off switch wire harness connector.

There should be continuity. If OK, go to Step 3. If not OK, repair the open circuit as required.

(3) Plug in the wire harness connectors at the low pressure cut-off and high pressure cut-off switches.

Connect the battery negative cable. Turn the ignition switch to the On position. Check for battery voltage at the fused ignition switch output (run) circuit cavity in the body half of the electronic cycling clutch switch wire harness connector. If OK, go to Step 4. If not OK, repair the open circuit to the junction block as required.

(4) Plug in the wire harness connector at the electronic cycling clutch switch. With the ambient temperature from 20 to 30 C (68 to 90 F), start the engine and set the heater-A/C mode control switch in any A/C position. If the compressor clutch fails to engage, use a DRBIIIt scan tool and the proper Diagnostic Procedures manual to check the Powertrain Control Module (PCM) and its inputs and outputs.

If the compressor clutch engages, the clutch should cycle on and off two to three times per minute. If the clutch fails to cycle at this rate in these ambient temperatures, replace the faulty electronic cycling clutch switch.

NOTE: If the ambient temperature is above 32 C (90 F) the compressor clutch may stay engaged and not cycle due to the high heat load. This condition is normal.

EXPANSION VALVE

These tests must be made at an ambient temperature of 21 to 29 C (70 to 85 F). Disconnect the wire connector at the low pressure cut off switch. Use a jumper wire to jumper terminals at the connector.

FRONT (ONLY)

(1) Attach a manifold gauge set. Close the vehicle doors and windows, start the engine, and hold the engine speed at 1,000 rpm. Set the heater-A/C mode control switch knob to the recirculation mode (Max A/C) position, the temperature control knob to the full hot position, and the blower motor switch to the highest speed position.

(2) Operate the air conditioning system for at least five minutes to stabilize the system, and to provide sufficient reheat to load the evaporator. The discharge pressure (high side) at the service port should reach 966 to 1656 kPa (140 to 240 psi). If this discharge pressure cannot be obtained, check the refrigerant system charge. See Refrigerant System Charge in the Service Procedures section of this group.

WARNING: EXTREME CARE MUST BE USED WHEN HANDLING LIQUID CARBON DIOXIDE (CO2), AS SKIN INJURY CAN OCCUR. PROTECTIVE GLOVES SHOULD BE WORN.

(3) Apply liquid carbon dioxide (CO2) to the expansion valve control head (completely cover the head) for a minimum of thirty seconds. Observe the manifold gauge set. The suction pressure (low side) must drop to below 50 kPa (7.25 psi). If this reading is not obtained, the expansion valve is faulty and must be replaced.

(4) Remove the liquid carbon dioxide (CO2) from the control head. Observe the manifold gauge set.

The suction pressure (low side) must increase to a minimum of 262 kPa (38 psi), and then stabilize to a pressure of 172 to 240 kPa (25 to 35 psi). If these readings are not obtained, the expansion valve is faulty and must be replaced.

(5) Set the engine idle speed at 1,000 rpm and the blower motor switch to the highest speed position.

The suction pressure (low side) should be 138 to 207 kPa (20 to 30 psi). If the discharge pressure (high side) is higher than 1656 kPa (240 psi), check for a restricted discharge line. Also check the engine cooling system for overheating, air trapped in the system, or a faulty fan drive. If the discharge pressure (high side) is less than 966 kPa (140 psi), check for a faulty compressor.

FRONT AND REAR A/C

(1) Attach a manifold gauge set. Close the vehicle doors and windows, start the engine, and hold the engine speed at 1,000 rpm. Set the heater-A/C mode control switch knob to the recirculation mode (Max A/C) position, the temperature control knob to the full hot position, and both the front and rear blower motor switches to their highest speed positions.

(2) Operate the air conditioning system for at least five minutes to stabilize the system, and to provide sufficient reheat to load the front and rear evaporators.

The discharge pressure (high side) at the service port should reach 966 to 1656 kPa (140 to 240 psi). If this discharge pressure cannot be obtained, check the refrigerant system charge. See Refrigerant System Charge in the Service Procedures section of this group.

WARNING: EXTREME CARE MUST BE USED WHEN HANDLING LIQUID CARBON DIOXIDE (CO2) AS SKIN INJURY CAN OCCUR. PROTECTIVE GLOVES SHOULD BE WORN.

(3) Both the front and rear expansion valves should be checked for correct operation. Apply liquid carbon dioxide (CO2) to the front expansion valve control head (completely cover the head) for a minimum of thirty seconds. Observe the manifold gauge set. The suction pressure (low side) must drop to below 50 kPa (7.25 psi). If this reading is not obtained, the expansion valve is faulty and must be replaced.

(4) Apply liquid carbon dioxide (CO2) to the front expansion valve control head (completely cover the head) for a minimum of thirty seconds. Remove the protective cover and apply liquid carbon dioxide (CO2) to the rear expansion valve control head.

Grasp the suction line (large line) off the evaporator with a bare hand and hold it for at least two minutes.

Use the same procedure with the front expansion valve. Grasp the suction line jumper below the expansion valve (before the rear suction line tee) with a bare hand and hold for at least two minutes.

When testing the front expansion valve, place the rear blower motor switch in the Off position.

(5) With a correctly operating expansion valve, the suction line will feel warm with the closing of the valve (cold applied). Then the line will cool sharply within two minutes as the valve opens. If this temperature change does not occur, the expansion valve is faulty and must be replaced.