Circuit Description
When an A/C mode is selected, the A/C control head or the A/C programmer supplies a 12 volt signal to the PCM A/C request input. The A/C compressor clutch relay is controlled by the PCM. The PCM provides a ground path for the A/C relay coil. When the A/C compressor relay is engaged battery voltage is supplied to the compressor clutch coil. The PCM will enable the A/C compressor clutch whenever the engine is running and the A/C has been requested unless one or more of the following conditions are present:
| • | Throttle angle is greater than 90%. |
| • | Ignition 1 voltage is below 10 volts. |
| • | Engine speed is greater than 4225 RPM for longer than 5 second. |
| • | Engine speed is greater then 5280 RPM for any amount of time. |
| • | IAT is less than 0°C (32°F). |
Any of the conditions described above will inhibit A/C compressor relay operation.
Diagnostic Aids
Check for the following conditions:
| • | Poor connection at the PCM. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. |
| • | Damaged harness. Inspect the wiring harness for damage. |
| • | If the harness appears to be OK, disconnect the PCM, turn the ignition ON and observe a voltmeter connected to the A/C relay control circuit at the PCM harness connector while moving connectors and wiring harnesses related to the A/C relay. A change in voltage will indicate the location of the malfunction. |
Check for conditions that will disable A/C operation:
| • | Throttle angle is greater than 90%. |
| • | Ignition 1 voltage is below 10 volts. |
| • | Engine speed is greater than 4225 RPM for longer than 5 seconds. |
| • | Engine speed is greater then 5280 RPM for any amount of time. |
| • | IAT is less than 0°C (32°F). |
Step | Action | Value(s) | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On-board-Board Diagnostic (OBD) System Check performed? | -- | Go to Powertrain OBD System Check | |||||||||
2 | Are any PCM or HVAC DTCs stored? | -- | Diagnose the applicable DTCs - Go to Powertrain Control Module Diagnostic Trouble Codes | |||||||||
3 |
Important: The following conditions must be met before continuing with this step:
Is the A/C Clutch engaged? | -- | ||||||||||
4 |
Is the A/C compressor clutch engaged? | -- | Go to Diagnostic Aids | |||||||||
5 | With the A/C mode still selected, observe the A/C Request display on the scan tool. Does the A/C Request display YES? | -- | ||||||||||
6 | Observe the A/C pressure sensor display on the scan tool. Does the A/C pressure sensor indicate a voltage between the specified values? | 0.4V - 4.6V | Go to Functional Check | |||||||||
7 |
Is high side refrigerant pressure within the specified values? | 35 psi - 440 psi | ||||||||||
8 |
Does the voltage measure near the specified value? | 0V | ||||||||||
9 |
If any resistance is higher than the specified value, locate and repair cause of high resistance in the circuit as necessary. Refer to Wiring Repairs . Was a problem found? | 5 ohms | ||||||||||
10 | Check for the following conditions:
If a problem is found, repair as necessary. Refer to Wiring Repairs . Was a problem found? | -- | ||||||||||
11 | Locate and repair short to voltage in the A/C refrigerant pressure signal circuit. Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||||
12 | Check the A/C Clutch fuse. Is the fuse blown? | -- | ||||||||||
13 |
Is the test lamp ON? | -- | ||||||||||
14 |
Is the test lamp ON? | -- | ||||||||||
15 |
Is the test lamp ON? | -- | ||||||||||
16 |
Is the A/C compressor clutch engaged? | -- | ||||||||||
17 |
Is the test lamp ON? | -- | ||||||||||
18 |
Is the test lamp ON? | -- | ||||||||||
19 |
Was a problem found? | -- | ||||||||||
20 |
Is the test lamp ON? | -- | ||||||||||
21 |
Does the test lamp flash? | -- | ||||||||||
22 |
Was a problem found? | -- | ||||||||||
23 |
Is the test lamp ON? | -- | ||||||||||
24 |
Was a problem found? | -- | ||||||||||
25 |
Does the A/C Request display Yes? | -- | Go to Functional Check | |||||||||
26 |
Is the A/C compressor clutch engaged? | -- | ||||||||||
27 |
Is the A/C compressor clutch engaged? | -- | ||||||||||
28 | Locate and repair short to voltage in the A/C compressor clutch feed circuit. Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||||
29 | Probe the A/C Compressor Relay Control Circuit in the Underhood Electrical Center with a test lamp to B+. Is the test lamp ON? | -- | ||||||||||
30 |
Is the test lamp ON? | -- | ||||||||||
31 | Locate and repair short to ground in the relay switch feed circuit . Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||||
32 |
Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||||
33 | Locate and repair the open in the relay switch feed. Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||||
34 | Locate and repair the open in the B+ feed to the A/C compressor clutch coil. Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||||
35 | Locate and repair the open in the A/C compressor clutch ground. Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||||
36 | Locate and repair the open in the relay coil feed. Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||||
37 | Locate and repair the short to voltage in the A/C relay control circuit. Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||||
38 | Locate and repair the short to ground in the A/C relay control circuit. Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||||
39 | Replace A/C Compressor Clutch Assembly. Refer to Compressor Clutch Plate/Hub Assembly Install (V5 - Conventional Mount) . Is action complete? | -- | -- | |||||||||
40 | Replace the A/C compressor clutch coil. Refer to Compressor Clutch Coil Removal (V5 - Conventional Mount) . Is action complete? | -- | -- | |||||||||
41 | Replace the A/C Refrigerant Pressure Sensor. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement . Is action complete? | -- | -- | |||||||||
42 | Replace the A/C relay. Is action complete? | -- | -- | |||||||||
43 |
Important: Replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is action complete? | -- | -- | |||||||||
44 |
Important: The following conditions must be met before continuing with this step:
Is the A/C clutch engaged? | -- | System OK |
