For 1990-2009 cars

### Test Description

The number below refers to the step number on the diagnostic table.

1. This action will disable the HVAC control module output to evaporator temperature sensor.

Step | Action | Yes | No
--- | --- | --- | ---
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views DEFINITION: The A/C compressor clutch will not disengage when an A/C request has not been made and a Powertrain DTC has not been set.
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 |

1. Start the engine.
2. Place the blower motor switch in the OFF position.

Is the A/C compressor clutch engaged?

Go to Step 3

Go to Testing for Intermittent Conditions and Poor Connections

3 | With a scan tool, observe the A/C Request Signal parameter in the Body Control Module Input data list. Does the scan tool indicate the A/C Request Signal parameter is Yes? | Go to Step 5 | Go to Step 4
4 | Disconnect the A/C compressor clutch relay. Does the A/C compressor clutch disengage? | Go to Step 9 | Go to Step 6
5 | Disconnect the evaporator temperature sensor. Does the A/C compressor clutch disengage? | Go to Step 7 | Go to Step 8
6 | Test the supply voltage circuit of the A/C compressor clutch for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 17 | Go to Step 10
7 | Test the A/C request signal circuit of the HVAC control module for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 17 | Go to Step 11
8 | Test the A/C request signal circuit of the body control module (BCM) for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 17 | Go to Step 12
9 | Inspect for poor connections at the A/C compressor clutch relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 17 | Go to Step 13
10 | 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 . Did you find and correct the condition? | Go to Step 17 | Go to Step 14
11 | 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 . Did you find and correct the condition? | Go to Step 17 | Go to Step 15
12 | Inspect for poor connections at the harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 17 | Go to Step 16
13 | Replace the A/C compressor clutch relay. Refer to Compressor Relay Replacement . Did you complete the replacement? | Go to Step 17 | --
14 | Replace the A/C compressor. Refer to Air Conditioning Compressor Replacement . Did you complete the replacement? | Go to Step 17 | --
15 | Replace the HVAC control module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 17 | --
16 | Replace the BCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 17 | --
17 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 3