Chart C-10B A/C Clutch Circuit Diagnosis (C68 & CJ2 A/C)

Chart C-10B, A/C Clutch Circuit Diagnosis (Part 2 Of 3):

Chart C-10B, A/C Clutch Circuit Diagnosis (Part 3 Of 3):

A/C Clutch Circuit:

*** This information has been updated according to Technical Service Bulletin #416524, dated Sept. 1994.

CIRCUIT DESCRIPTION
The A/C relay is PCM controlled to delay A/C clutch engagement .4 second after A/C is turned "ON." This allows the IAC to adjust engine RPM before the A/C clutch engages. The PCM also causes the relay to disengage the A/C clutch during WOT operation. The A/C relay is energized when the PCM provides a ground path for CKT 459. The PCM may apply the A/C clutch during cranking to prevent A/C slugging during start-up.

TEST DESCRIPTION (Part 1 of 3)
Number(s) below refer to circled number(s) on the diagnostic chart part 1 of 3.
1. Determines whether or not the PCM recognizes the A/C request signal.
2. Checks for an open high pressure cutout switch.
3. Ensures that the HVAC programmer is supplying the A/C request signal.

TEST DESCRIPTION (Part 2 of 3)
Number(s) below refer to circled number(s) on the diagnostic chart part 2 of 3.
1. Determines whether the A/C relay can be controlled by the PCM.
2. Checks for ignition feed to relay contacts.
3. Determines whether problem is caused by relay, relay connections, clutch, or clutch circuitry.

TEST DESCRIPTION (Part 3 of 3)
Number(s) below refer to circled number(s) on the diagnostic chart part 3 of 3.
1. Determines whether or not the PCM is turning the A/C relay "ON" due to a false A/C request.
2. Isolates problem between the A/C control head and CKTs 604 and 762 to the high pressure cutout switch or CKT 204 and the PCM.
3. Checks for CKT 59 shorted to B+ or a faulty compressor clutch.
4. Determines whether the A/C relay is faulty or the A/C relay control circuit (CKT 459) is grounded all the time.