Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

DEFINITION: The A/C compressor clutch will not engage if an A/C request has been made, and a Engine Control DTC has not been set.

1

Did you perform the Diagnostic System Check-Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

1. Start the engine.
2. Observe the instrument panel coolant temperature gage.

Is the engine coolant temperature gage indicating an overheat status?

Go to Engine Overheating in Engine Cooling

Go to Step 3

3

Important: For A/C compressor operation, the ambient air temperature must be above 4°C (40°F).

1. Start the engine.
2. Place the blower motor switch in the maximum speed position.
3. Place the A/C request switch in the ON position.
4. Place the air temperature switch in the coldest position.

Does the A/C compressor clutch engage?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 4

1. Park the vehicle inside or out of direct sunlight.
2. Open the window in order to ventilate the interior of the vehicle.
3. If the A/C system was operating, then wait for approximately 2 minutes.
4. Turn OFF the ignition.
5. Install the J 43600 ACR 2000 Air Conditioning Service Center.
6. Record the ambient air temperature at the vehicle.
7. Record readings of the low and high side STATIC pressures.
8. Compare the low side pressure values and the high side pressure values with the allowable limits for the recorded ambient air temperature. Refer to Air Conditioning (A/C) System Performance Test in Heating, Ventilation and Air Conditioning.

Are the pressure values within the allowable limits for the recorded ambient air temperature, and within 103 kPa (15 psi) of each other?

Go to Step 5

Go to Leak Testing in Heating, Ventilation and Air Conditioning

5

1. Start the engine.
2. With a scan tool, observe the A/C refrigerant pressure sensor voltage parameter in the Engine Control Module General Info Inputs/Outputs data list.

Does the scan tool indicate voltage?

Go to Step 6

Go to Step 20

Is the HVAC control assembly inoperative?

Go to Step 15

Go to Step 7

1. Start the engine.
2. With a scan tool, observe the A/C request signal parameter in the Engine Control Module, General Info Inputs/Outputs data list.
3. Place the air temperature switch in the coldest position.
4. Place the A/C request switch in the ON position.

Does the scan tool indicate that the A/C request signal parameter is YES?

Go to Step 9

Go to Step 8

1. Turn OFF the ignition.
2. Test the A/C request signal circuit for a short to voltage, high resistance, or for an open. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 34

Go to Step 28

With a scan tool, command the A/C compressor clutch relay ON and OFF.

Does the clutch relay turn ON and OFF with each command?

Go to Step 10

Go to Step 14

1. Turn OFF the ignition.
2. Disconnect the A/C compressor clutch relay.
3. Turn ON the ignition, with the engine OFF.
4. Probe the coil side of the voltage supply circuit with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 11

Go to Step 23

1. Connect a test lamp between the control circuit and the coil side of the voltage supply circuit.
2. With a scan tool, command the A/C compressor clutch relay ON and OFF.

Does the test lamp turn ON and OFF with each command?

Go to Step 25

Go to Step 12

Does the test lamp remain illuminated with each command?

Go to Step 18

Go to Step 17

1. Turn OFF the ignition.
2. Disconnect the A/C compressor clutch relay.
3. Probe the switch side of the voltage supply circuit with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 14

Go to Step 22

1. Connect a 10-amp fused jumper between the switch side voltage circuit of the clutch relay and the supply voltage circuit of the clutch.
2. Turn ON the ignition, with the engine OFF.

Does the A/C compressor clutch engage?

Go to Step 25

Go to Step 19

Test the ignition 3 voltage circuit of the HVAC control assembly for a short to ground, for a high resistance, or for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 34

Go to Step 16

Test the ground circuit of the HVAC control assembly for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 34

Go to Step 27

Test the control circuit of the relay for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 34

Go to Step 28

Test the control circuit of the relay for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 34

Go to Step 28

Test the supply voltage circuit at the relay for a short to ground, for a high resistance, or for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 34

Go to Step 21

Test the ground circuit of the A/C refrigerant pressure sensor for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 34

Go to Step 24

Test the ground circuit of the A/C compressor clutch for a high resistance or for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 34

Go to Step 26

Repair the switch side voltage supply circuit of the relay. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 34

--

Repair the coil side of the voltage supply circuit of the relay. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 34

--

Inspect for poor connections at the harness connector of the A/C refrigerant pressure sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 34

Go to Step 29

Inspect for poor connections at the relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 34

Go to Step 30

Inspect for poor connections at the harness connector of the A/C compressor clutch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 34

Go to Step 31

Inspect for poor connections at the harness connector of the HVAC control assembly. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 34

Go to Step 32

Inspect for poor connections at the harness connector of the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 34

Go to Step 33

Replace the A/C Refrigerant Pressure Sensor. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement in Heating, Ventilation, and Air Conditioning.

Did you complete the replacement?

Go to Step 34

--

Replace the relay.

Did you complete the replacement?

Go to Step 34

--

Replace the A/C compressor clutch. Refer to Compressor Clutch Assembly Replacement in Heating, Ventilation, and Air Conditioning.

Did you complete the replacement?

Go to Step 34

--

Replace the HVAC control assembly. Refer to Heater and Air Conditioning Control Replacement

Did you complete the replacement?

Go to Step 34

--

Replace the ECM. Refer to Control Module References in Computer/Integrating Systems for Replacement, Setup, and Programming.

Did you complete the replacement?

Go to Step 34

--

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 4