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. Install a scan tool.
2. Start the engine
3. With a scan tool, observe the engine coolant temperature sensor (ECT) parameter in the Powertrain data list.

Does the scan tool indicate that the ECT parameter is above 124°C (255°F)?

Go to Engine Overheating in Engine Cooling

Go to Step 3

3

Important: For A/C compressor operation, 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 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, 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 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 in Heating, Ventilation and Air Conditioning.

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 within the 103 kpa (15 psi) of each other?

Go to Step 6

Go to Step 16

6

The HVAC control module is inoperative when the module does not respond to any operator control requests.

Is the HVAC control module inoperative?

Go to Step 15

Go to Step 7

1. Start the engine.
2. With a scan tool, observe the A/C request parameter in the Powertrain 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 parameter is YES?

Go to Step 8

Go to Step 27

With a scan tool, observe the A/C Relay Command status in the Powertrain Data List.

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

Go to Step 9

Go to Step 28

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 13

Go to Step 10

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 11

Go to Step 23

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 25

Go to Step 12

Does the test lamp remain illuminated with each command?

Go to Step 19

Go to Step 18

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 14

Go to Step 22

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 25

Go to Step 20

Test the ignition 3 voltage circuit of 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 34

Go to Step 17

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 34

Go to Step 24

Test the ground circuit of the HVAC control module 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 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 34

Go to Step 28

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 34

Go to Step 28

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 34

Go to Step 21

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 34

Go to Step 26

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 34

--

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 34

--

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 34

Go to Step 29

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 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 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 34

Go to Step 32

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 34

Go to Step 33

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 34

--

Replace the A/C compressor clutch relay.

Did you complete the replacement?

Go to Step 34

--

Replace the A/C compressor clutch coil. Refer to Air Conditioning Clutch Coil Removal and Air Conditioning Clutch Coil Installation in Heating, Ventilation, and Air Conditioning.

Did you complete the replacement?

Go to Step 34

--

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

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

Did you complete the replacement?

Go to Step 34

--

Important:  Perform the reprogramming procedure for the PCM.

Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls-3.5L.

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