Part 2 of 2

A/C Clutch Control Diagnosis (Part 2 Of 2):

A/C Clutch Control Diagnosis:

CIRCUIT DESCRIPTION
When the A/C control switch is turned "ON," voltage is supplied to the Vehicle Control Module-A (VCM-A) on CKT 66. If there is sufficient pressure in the A/C system and/or the ambient temperature is not too cold, the A/C pressure switch will close and supply voltage to the switch side of the A/C relay on CKT 901. After a calibrated delay time (approximately 20 sec), the VCM-A will ground CKT 459, enabling the relay and applying voltage to CKT 248. The normally closed A/C high pressure cutoff switch will provide voltage to CKT 59 and enable the A/C clutch. Voltage is also supplied to the VCM-A on CKT 59. This voltage signal allows the VCM-A to make idle, timing and fuel corrections for smoother clutch engagements.

CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. Checks for voltage at relay.
2. Checks CKT 248 and the relay.
3. Checks CKT 66.
4. Checks CKT 59 and high pressure switch.
5. Checks state of charge CKT 901 and low pressure switch.

DIAGNOSTIC AIDS
Make sure that the correct A/C relay is installed on the vehicle.