System Diagnosis

NOTE: The following procedures assume that the System Check under Blower Controls has been completed and that those tests indicated the compressor may not be operating correctly.

Motor idling and temperature outside car at 60 °F or higher. Set Mode Selector to MAX and Temperature Lever to COLD.

1. Measure voltage to ground at the DK GRN wire (terminal B) of the the Compressor Clutch. If voltage is zero, proceed to Step 2. If Battery voltage is present, make the following checks:

^ Temporarily ground the BLK/WHT wire (terminal A) of the Compressor Clutch with a fused jumper. If the clutch does not engage and connector pins are not loose, replace the clutch.
^ Measure voltage to ground at BLK/ WHT wire (terminal A) of the Compressor Clutch. If Battery voltage is present, check for an open at the A/C High Pressure Cut-Off Switch, then check for an open in the wiring to ground (wire 150).
^ If the A/C High Pressure Cut-Out Switch is open, check that the cooling fan operates when the compressor is turned on and that there is no obstruction to air flow through the condenser.
^ If cooling fan operates with compressor,replace the A/C High Pressure Cut-Out Switch.

2. Measure voltage to ground at the LT BLU wire (terminal B) of the A/C Cut-Out Relay and connector C1(terminal B8) of the ECM. If voltage is zero at both terminals, proceed to Step 3. If Battery voltage is present, make the following tests:

^ Measure voltage to ground at the DK GRN wire (terminal D) of the A/C Cut-Out Relay. If Battery voltage is present, check for an open or faulty connector pin in the wiring between this point and the A/C Compressor Clutch (wire 59).
^ If Battery voltage is not present at the DK GRN wire of the A/C Cut-Out Relay, measure the voltage at the PPL wire (terminal A) of the relay. If the voltage is zero, check the Power Steering Pressure Switch, wiring to ECM/ERLS Fuse, and the ECM/ERLS Fuse. If the Power Steering Switch is open, replace it.
^ If Battery voltage is present at the PPL wire of the A/C Cut-Out Relay, measure the voltage to ground at the LT GRN/BLK wire (terminal C) of the A/C Cut-Out Relay. If Battery voltage is not present and relay connector pins are not loose, replace the A/C Cut-Out Relay. If voltage is present, refer to Powertrain Management / Computers and Controls / Procedures. Testing and Inspection

3. Measure the voltage to ground at the LT GRN wire of the Pressure Cycling Switch. If voltage is zero, proceed to Step 4. If Battery voltage is present, make the following tests:

^ Measure voltage to ground at the LT BLU wire of the Pressure Cycling Switch. If Battery voltage is present, repair open or faulty connector pin on wire 67.
^ If voltage at the LT BLU wire is zero and refrigerant pressure is normal, replace the Pressure Cycling Switch.

4. Measure voltage to ground at the BRN wire (terminal E) on the A/C Control Head. If voltage is zero check the HTR-A/C Fuse. If fuse is good, repair open in BRN wire (wire 50). If Battery voltage is present, proceed with the following tests:

^ Measure voltage to ground at the LT GRN wire (terminal C) on the A/C Control Head. If Battery voltage is present, repair open in the wiring between the A/C Control Head and the Pressure Cycling Switch (wire 66).
^ If the voltage at terminal C is zero, move the Mode Selector Switch through all positions. Check the voltage at terminal C at each position. Battery voltage should be present in MAX, NORM, BI-LEVEL, and DEF. If Battery voltage is not present in all these positions, replace the A/C Control Head.