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 96%. |
| • | A/C head pressure is greater than 440 psi (4.6 volts) or less than 35 psi (0.4 volt) (as determined by the A/C refrigerant pressure sensor). |
| • | Ignition 1 voltage is below 10.5 volts. |
| • | Engine speed is greater than 4300 RPM for longer than 1 second. |
| • | Engine speed is greater then 5400 RPM for any amount of time. |
| • | ECT is greater than 124°C (255°F). |
| • | IAT is less than 5°C (41°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 96%. |
| • | A/C head pressure is greater than 440 psi (4.6 volts) or less than 35 psi (0.4 volt) (as determined by the A/C refrigerant pressure sensor). |
| • | Ignition 1 voltage is below 10.5 volts. |
| • | Engine speed is greater than 4300 RPM for longer than 1 seconds. |
| • | Engine speed is greater then 5400 RPM for any amount of time. |
| • | ECT is greater than 124°C (255°F). |
| • | IAT is less than 5°C (41°F). |
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table:
-
The P1641 diagnostic handles the control portion of the relay circuit. The P0530 diagnostic pertains to the A/C refrigerant pressure sensor. If either DTC is set, perform that diagnostic first.
-
Under certain conditions, the PCM may engage the A/C compressor clutch briefly at start-up. Answer Yes to this step if the A/C compressor clutch remains engaged after the engine is started with all A/C controls in the Off Position.
If Refrigerant Pressure is low, go to Refrigerant System Checks in HVAC for diagnostic procedures.
-
Check for poor connections/terminal tension at the fuse. Refer to Intermittents and Poor Connections Diagnosis .
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||||
Is DTC P0530 or P1641 set? | -- | Go to the applicable DTC table | ||||||||
|
Important: The following conditions must be met before continuing with this step:
Is the A/C Clutch engaged? | -- | |||||||||
4 | Select an A/C mode on the HVAC control head. Is the A/C clutch engaged? | -- | Go to Diagnostic Aids | |||||||
5 | Does the scan tool indicate A/C Request Yes? | -- | ||||||||
Is the fuse OK? | -- | |||||||||
7 |
Is the resistance more than the specified value? | 2 Ohms | ||||||||
8 |
Is the resistance more than the specified value? | 2 Ohms | ||||||||
9 |
Is the fuse OK? | -- | ||||||||
10 |
Is the fuse OK? | -- | Go to Diagnostic Aids | |||||||
11 |
Is the test lamp on? | -- | ||||||||
12 | Connect the power feed circuit to the compressor clutch feed circuit in the relay connector using a 10 Amp fused jumper. Does the A/C compressor clutch engage? | -- | ||||||||
13 |
Is the test light on? | -- | ||||||||
14 |
Is the test light on? | -- | ||||||||
15 | Disconnect the A/C compressor clutch control relay. Is the A/C compressor still engaged? | -- | ||||||||
16 | Using test light J 35616-200 connected to ground, probe the A/C compressor clutch feed circuit in the relay connector. Is the test light on? | -- | Mechanical A/C clutch failure--Go to Compressor Clutch Plate and Hub Assembly Removal (V5 - Conventional Mount) | |||||||
17 | Repair the short to ground in the power feed circuit to the relay. Is the action complete? | -- | -- | |||||||
18 | Repair the short to ground in the compressor clutch feed circuit. Is the action complete? | -- | -- | |||||||
19 | Repair the open/high resistance power feed circuit to the relay. Is the action complete? | -- | -- | |||||||
20 | Repair the open/high resistance A/C compressor clutch feed circuit. Is the action complete? | -- | -- | |||||||
21 | Repair the open/high resistance A/C compressor clutch ground circuit. Is the action complete? | -- | -- | |||||||
22 | Repair the short to power in the A/C compressor clutch feed circuit. Is the action complete? | -- | -- | |||||||
23 | Check for poor connections/terminal tension at the relay connector. Refer to Intermittents and Poor Connections Diagnosis . Was a problem found and corrected? | -- | ||||||||
24 | Replace the relay. Is the action complete? | -- | -- | |||||||
25 | Check for poor connections/terminal tension at the A/C compressor clutch connector. Refer to Intermittents and Poor Connections Diagnosis . Was a problem found and corrected? | -- | ||||||||
26 | Replace the A/C compressor clutch coil. Is the action complete? | -- | -- | |||||||
27 |
Important: The following conditions must be met before continuing with this step:
Does the A/C compressor clutch engage and disengage? | -- | System OK |
