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 compressor clutch. If voltage is zero, proceed to Step 2. If Battery voltage is present, make the following checks:

^ Temporarily ground the BLK 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 wire (terminal A) of the compressor clutch. If Battery voltage is present, check for an open in the wiring to ground (wire 150).

2. Measure voltage to ground at the DK GRN/ WHT wire (terminal B) of the A/C Compressor Control Relay. If voltage is zero, 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 Compressor Control 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 (terminal D) of the A/C Compressor Control Relay measure the voltage to ground at the PNK/BLK wire (terminal A). If no voltage is present at the PNK/BLK wire (terminal A) then check wiring back to Fuse Block.
^ If Battery voltage is present at the PNK/BLK wire (terminal A) measure voltage from PNK/BLK wire (terminal A) to the DK BLU wire (terminal C).
^ If Battery voltage is present between the PNK/BLK wire (terminal A) and the DK BLU wire (terminal C) replace the A/C Compressor Control Relay.
^ If the voltage between the PNK/BLK wire and the DK BLU wire of the A/C Compressor Control Relay is zero refer to Powertrain Management/Computers and Controls. Testing and Inspection
3. Measure voltage to ground at the LT/GRN wire (terminal A) of the A/C Low Pressure 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/BLK wire (terminal 13) of the A/C Low Pressure Switch. If battery voltage is present repair open or faulty connector pin in wire 67.
^ If voltage at the LT BLU/BLK wire is zero and refrigerant pressure is normal, replace the A/C Low Pressure Switch.
^ Measure voltage to ground at LT BLU/ BLK wire (terminal B) of A/C High Pressure Cut-Off Switch. If voltage is ground, repair open or faulty connector pin in wire 67.
^ If Battery voltage is present at the LT BLU/BLK wire, measure the voltage to ground at the DK GRN/WHT wire (terminal A) of the A/C High Pressure Cut-Off Switch. If Battery voltage is present, this position of the compressor contact circuit is good.
^ If the voltage to ground at the DK GRN/WHT wire is zero, check that the engine cooling fan operates when the compressor is turned on and that there is no obstruction to air flow through the condenser. If the condenser cooling is satisfactory, replace the A/C High Pressure Cut-Off 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 the 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 A/C Low Pressure Switch.
^ 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.