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.

1

Did you perform the HVAC Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Automatic

2

1. Start the engine.
2. Observe the coolant temperature indicator.

Is the engine coolant temperature indicator illuminated?

Go to Engine Coolant Temperature Indicator Always On in Engine Cooling

Go to Step 3

3

Important: 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. Press the A/C switch to 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 4

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, allow the A/C system to equalize (about 2 minutes).
4. Turn OFF the ignition.
5. Install the J 43600 ACR 2000.
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 low and high side 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

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 with 103 kpa (15 psi) of each other?

Go to Step 6

Go to Step 21

6

Is the HVAC control module (IPM) inoperative?

Go to Step 20

Go to Step 7

1. Start the engine.
2. With a scan tool, observe the A/C Relay Command parameter in the Powertrain data list.
3. Place the air temperature switch in the coldest position.
4. Press the A/C switch to the ON position.

Does the scan tool indicate that the A/C Relay Command parameter is ON?

Go to Step 14

Go to Step 8

With a scan tool, observe the A/C Clutch (desired) parameter in the dash integration module (DIM) A/C Information list.

Does the scan tool indicate that the A/C Clutch (desired) parameter is ON?

Go to Step 9

Go to Step 10

With a scan tool, observe the A/C Clutch (actual) parameter in the DIM A/C Information list.

Does the scan tool indicate that the A/C Clutch (actual) parameter is ON?

Go to Step 14

Go to Step 34

With a scan tool, observe the Control Head (desired) parameter in the DIM A/C Information list.

Does the scan tool indicate that the Control Head (desired) parameter is ON?

Go to Step 11

Go to Step 13

With a scan tool, observe the Pressure Status parameter in the DIM A/C Information list.

Does the scan tool indicate that the Pressure Status parameter is Normal?

Go to Step 12

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

With a scan tool, observe the Temperature Status parameter in the DIM A/C Information list.

Does the scan tool indicate that the Temperature Status parameter is OK?

Go to Step 31

Go to Engine Overheating in Engine Cooling

1. With a scan tool, observe the Control Head (desired) parameter in the DIM A/C information list.
2. Place the mode switch in the defrost position.

Does the scan tool indicate that the Control Head (desired) parameter turn ON and OFF with each command?

Go to Step 31

Go to Step 33

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 18

Go to Step 15

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 16

Go to Step 28

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 30

Go to Step 17

Does the test lamp remain illuminated with each command?

Go to Step 24

Go to Step 23

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 19

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 30

Go to Step 25

Test the ignition voltage circuit to the IPM 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 41

Go to Step 22

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 41

Go to Step 29

Test the ground circuit to the IPM for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 41

Go to Step 33

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 41

Go to Step 34

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 41

Go to Step 34

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 41

Go to Step 26

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 41

Go to Step 32

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 41

--

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 41

--

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 41

Go to Step 36

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 41

Go to Step 37

Inspect for poor connections at the DIM. 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 41

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 41

Go to Step 38

Inspect for poor connections at the harness connector of the IPM. 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 41

Go to Step 39

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 41

Go to Step 40

Replace the DIM. Refer to Dash Integration Module Replacement in Body Control System.

Did you complete the replacement?

Go to Step 41

--

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 41

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Replace the A/C compressor clutch relay.

Did you complete the replacement?

Go to Step 41

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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 41

--

Important: Perform the recalibration procedure for the HVAC control module.

Replace the IPM. Refer to HVAC Control Module Replacement .

Did you complete the replacement?

Go to Step 41

--

Important:  Perform the reprogramming procedure for the PCM.

Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls-4.6L.

Did you complete the replacement?

Go to Step 41

--

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 4