Schematic Reference: HVAC Schematics

DEFINITION: The A/C compressor clutch will not engage when an A/C request has been made and a Powertrain DTC has not been set.

Did you review the HVAC operation and perform the necessary inspections?

Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Manual

2

Important: The ambient air temperature must be above 3°C (38°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 operate?

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

Go to Step 3

1. Park the vehicle inside or in the shade.
2. Open the windows in order to ventilate the interior of the vehicle.
3. If the A/C system was operating, then allow the A/C system to equalize for approximately 2 minutes.
4. Ensure that the ignition key is in the OFF position.
5. Install the J 43600 .
6. Record the ambient air temperature at the vehicle.
7. Record readings of the low and high side STATIC pressures.
8. Compare the low and high side pressure values with the allowable limits for the recorded ambient air temperature. Refer to Air Conditioning (A/C) System Performance Test .

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

Go to Step 4

Go to Leak Testing in Heating, Ventilation and Air Conditioning

1. Turn ON the ignition, with the engine OFF.
2. With a scan tool, observe the A/C high side pressure sensor parameter in the powertrain data list.
3. Compare the A/C high side pressure on the scan tool to the high side pressure value on the ACR2000.

Are the high side pressure values within 103 kpa (15 psi) of each other?

Go to Step 5

Go to Step 20

5

Is the HVAC control assembly inoperative?

Go to Step 19

Go to Step 6

1. Start the engine.
2. With a scan tool, observe the A/C Request Signal parameter in the powertrain engine data list.
3. Place the air temperature switch in the coldest position.
4. Turn the blower motor to the on position.
5. Place the A/C request switch in the ON position.

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

Go to Step 13

Go to Step 7

Does the A/C request indicator illuminate?

Go to Step 9

Go to Step 8

Important: The blower motor must be in the ON position for this step.

1. Turn ON the ignition.
2. Test the OFF blower motor control circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 40

Go to Step 32

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

Did you find and correct the condition?

Go to Step 40

Go to Step 10

1. Disconnect the evaporator temperature sensor.
2. Measure the resistance of the evaporator temperature sensor. Refer to the Sensor Resistance Table .

Does the resistance measure near the values specified in the sensor resistance table?

Go to Step 11

Go to Step 30

Test the evaporator temperature signal circuit for a short to ground, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 40

Go to Step 12

Test the evaporator temperature sensors low reference circuit for a short to ground, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 40

Go to Step 32

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

Does the A/C compressor clutch relay turn ON and OFF with each command?

Go to Step 17

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 voltage supply circuit of the A/C compressor clutch relay with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 15

Go to Step 26

1. Connect a test lamp between the control circuit of the A/C compressor clutch relay and the coil side voltage supply circuit of the A/C compressor clutch relay.
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 27

Go to Step 16

Does the test lamp remain illuminated with each command?

Go to Step 23

Go to Step 22

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

Does the test lamp illuminate?

Go to Step 18

Go to Step 27

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

Does the A/C compressor clutch engage?

Go to Step 29

Go to Step 24

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

Did you find and correct the condition?

Go to Step 40

Go to Step 21

Test the ground circuit of the A/C 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 40

Go to Step 28

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 40

Go to Step 32

Test the control circuit of the A/C compressor clutch relay for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 40

Go to Step 33

Test the control circuit of the A/C compressor clutch 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 40

Go to Step 33

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

Did you find and correct the condition?

Go to Step 40

Go to Step 25

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

Did you find and correct the condition?

Go to Step 40

Go to Step 31

Repair the switch side voltage supply circuit of the A/C compressor clutch relay. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 40

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Repair the coil side voltage supply circuit of the A/C compressor clutch relay. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 40

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Inspect for poor connections at the harness connector of the A/C High 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 40

Go to Step 34

Inspect for poor connections at the A/C compressor clutch 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 40

Go to Step 36

Inspect for poor connections at the evaporator temperature 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 40

Go to Step 35

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 39

Go to Step 37

Inspect for poor connections at the harness connector of the HVAC control module. 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 40

Go to Step 38

Inspect for poor connections at the harness connector of the powertrain control module (PCM). 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 40

Go to Step 39

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

Did you complete the replacement?

Go to Step 40

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Replace the evaporator temperature sensor. Refer to Evaporator Temperature Sensor Replacement in Heating, Ventilation and Air Conditioning.

Did you complete the replacement?

Go to Step 40

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Replace the A/C compressor clutch relay.

Did you complete the replacement?

Go to Step 40

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

Did you complete the replacement?

Go to Step 40

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Replace the HVAC control module. Refer to HVAC Control Module Replacement .

Did you complete the replacement?

Go to Step 40

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Important:  Perform the programming procedure for the PCM.

Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls-3.4L

Did you complete the replacement?

Go to Step 40

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Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3