Flow Chart No.5: A/C Operates Improperly

Step 1 Check system operation.





1. Set function selector lever at an A/C position.
2. Turn ignition switch to RUN position.
3. Does A/C clutch engage?
^Yes Clutch circuit OK.
^No Go to Step 2.

Step 2 Check for voltage.





1. Check for voltage at circuit wire at the A/C cycling switch.
2. Is voltage present?
^Yes Go to Step 3.
^No Go to Step 8.

Step 3 Bypass A/C clutch cycling pressure switch.
1. Disconnect connector at A/C cycling switch.
2. Jumper connector pins.
3. A/C clutch should engage.
4. Does A/C clutch engage?
^Yes Go to Step 4.
^No Go to Step 5.

Step 4 Check system pressure.
1. Connect manifold gauge set and check system pressure.
2. Is pressure above 55 psi (ambient temperature above 50°F)?
^Yes Replace A/C cycling pressure switch. Go to Step 1.
^No Check refrigerant system for leaks. Repair and charge system as necessary.
Go to Step 1.

Step 5 Check voltage at clutch.



1. Check for voltage at A/C clutch field coil (B/Y wire).
2. Is voltage present?
^Yes Go to Step 6.
^No Go to Step 7.

Step 6 Check clutch ground.



1. Jumper ground terminal of A/C clutch field coil to ground.
2. Does A/C clutch engage?
^Yes Service open in ground wire. Go to Step 1.
^No Replace A/C clutch field coil. Go to Step 1.

Step 7 Check fuse.
1. Does fuse have continuity?
^Yes Go to Step 8.
^No Check for short. Service as necessary. Replace fuse.
Go to Step 1.

Step 8 Check A/C controls.



1. Move function selector switch to DEFROST position.
2. Check for voltage at R/Y wire at the connector of A/C cycling switch.
3. Is voltage present?
^Yes Go to Step1O.
^No Go to Step 9.

Step 9 Check ground wire (B).
1. Remove connector from control function selector switch.




2. Check for voltage at circuit.
3. Is voltage present?
^Yes Condition may be intermittent. Attempt to recreate condition by wiggling harness at connectors, crimps, etc. Service all conditions located. Verify operation.
^No Check for open circuit in W/PU wire. Service as necessary.
Go to Step 1.

Step 10 Check A/C function switch.
1. Check A/C function switch for continuity.

Note: Function switch must be in DEFROST position.

2. Is there continuity through function switch only?
^Yes Replace A/C function switch. Go to Step 1.
^No Check for open PU wire between A/C control and A/C cycling switch. Service as necessary.
Go to Step 11.

Step 11 Check system voltage.
1. Check for voltage to control head (blower motor should run).
2. Is voltage present?
^Yes Go to Step l2.
^No Check for open circuit. Repair as required.

Step 12 Check vehicle accessory voltage.
1. Check for power at RUN terminal of ignition switch (turn on another accessory).
2. Is voltage present at ignition switch?
^Yes Go to Step 13.
^No Service ignition switch.
Go to Step 1.

Step 13 Check belt tension.
1. Check accessory drive belt tension.
2. Is drive belt tension to specifications?
^Yes Go to Step 14.
^No Service drive belt as necessary.

Step 14 Check for seized compressor.
1. Perform Rotating Torque Check.
Required rotating torque, 2nd revolution: 13 N.m (9.6 ft.lbs)
2. Does A/C compressor pass test?
^Yes Refer to Troubleshooting Chart.
^No Replace A/C compressor. Go to Step 1.