Chart C-10A A/C Clutch Circuit Diagnosis (C61 & C67 A/C)

Chart C-10A, A/C Clutch Circuit Diagnosis (Part 1 Of 3):

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

Chart C-10A, 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 0.4 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 startup.

TEST DESCRIPTION (Part 1 of 3)
Number(s) below refer to circled number(s) on the diagnostic chart.
1. A/C clutch should not be engaged with the engine running if an A/C mode is not selected at the control head.
2. Compressor clutch should apply if the conditions under the NOTICE at the top of the chart have been met.
3. Checks for an A/C request signal from the control head to the pressure cycling switch.

TEST DESCRIPTION (Part 2 of 3)
Number(s) below refer to circled number(s) on the diagnostic chart.
1. Checks for ignition voltage (CKT 639) to terminal "86" of relay, and checks PCM control of the ground circuit (CKT 459) for the A/C relay coil.
2. Checks for ignition voltage to the A/C relay contacts (CKT 639 to relay terminal "30").
3. Determines whether the A/C relay or the compressor clutch coil or circuitry is at fault.


TEST DESCRIPTION (Part 3 of 3)
Number(s) below refer to circled number(s) on the diagnostic chart.
1. Determines whether or not the PCM is turning the A/C relay "ON" due to a false A/C request.
2. Isolates problem to the A/C control head and CKTs 604 and 762 to the pressure cycling switch or CKT 204 to 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.