A/C System
A/C operation is requested by the ACM using a serial data (Class 2) message to the PCM. The PCM will ground the A/C relay allowing current to flow through the A/C Compressor clutch coil. The PCM will disable or inhibit A/C compressor clutch operation during the following conditions:
| • | High power steering load indicated |
| • | Engine not running |
| • | Engine at wide open throttle |
| • | Outside temperature below approximately 4°C (40°F) |
| • | Certain PCM DTCs set |
The PCM will also engage the A/C compressor clutch during cranking in colder weather to prevent A/C slugging.
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
-
Since many DTCs disable A/C clutch operation, any DTCs must be repaired and cleared before using this table.
-
An A/C Relay status of OFF indicates that the PCM is not allowing A/C clutch operation (DTCs set or low outside temp. etc.) or the ACM is not requesting A/C operation from the PCM. Check for HVAC DTC's which may inhibit the ACM from requesting A/C clutch operation.
To verify PCM control of the A/C clutch, use the output test for the A/C relay and command the A/C clutch ON and OFF with the engine RUNNING. Watch for the A/C clutch to engage and disengage.
-
Refer to the HVAC section for diagnosis of intermittent operation. Check for proper system pressures and for HVAC DTC's that may be stored indicating a previous fault condition.
-
A lighted test light indicates the PCM can control the A/C relay ON. No A/C clutch operation could be caused by a blown fuse, a defective relay, A/C system pressure faults which open one of the A/C pressure switches or a defective A/C compressor clutch coil or ground. Refer to the HVAC section for diagnosis of these components.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||||||||
Does the display indicate the A/C relay is requested ON? | -- | Go to Test Description | ||||||||
3 | Observe the operation of the A/C clutch. Is the A/C clutch engaged? | -- | ||||||||
Does the compressor clutch operate while requested OFF? | -- | Go to Test Description | ||||||||
Is the test light illuminated? | -- | Go to Test Description | ||||||||
6 | Using a test light connected to a good GROUND, probe the A/C Compressor Clutch relay terminal D1. Is the test light illuminated? | -- | ||||||||
7 |
Is the resistance the same or less than the value specified? | 5 ohms | ||||||||
8 | Repair the open in the A/C Compressor Clutch Control circuit. Is the repair complete? | -- | -- | |||||||
9 | Check for the following conditions and repair as necessary:
Was any of the above conditions located and repaired? | -- | ||||||||
10 | Repair the short to voltage on the A/C compressor clutch relay control circuit. Is the repair complete? | -- | -- | |||||||
11 |
Was a repair made to the terminal contact at either connector? | -- | ||||||||
12 | Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the replacement complete? | -- | -- |
