COMPRESSOR CLUTCH CIRCUIT DIAGNOSIS
1. Check For Voltage Ensure ignition switch is in RUN position and A/C system is in defrost position. Check for voltage at A/C clutch cycling pressure switch Purple wire (located on accumulator-drier). If 10 volts or greater exists, go to next step. If less than 10 volts exists, go to step 9)
2. By-Pass Clutch Cycling Pressure Switch Disconnect clutch cycling pressure switch. Ensure engine is running and A/C control panel is set to maximum cooling position. Connect jumper wire across switch harness connector terminals. If the clutch engages, go to step 4). If the clutch does not engage, go to next step.
3. Check A/C High Pressure Cut-Off Switch Using an ohmmeter, check for continuity between A/C high pressure cut-off switch terminals. If continuity exists, go to step 6). If continuity does not exist, replace A/C high pressure cut-off switch and return to step 1).
4. Check Refrigerant Pressure Connect manifold gauge set and note pressure readings. If pressure reading is less than 55 psi (3.9 kg/cm 2 ), check system for leaks and repair as required. After repairs, verify A/C system operation. If pressure reading is greater than 55 psi (3.9 kg/cm 2 ), replace clutch cycling pressure switch and verify A/C system operation.
5. Check A/C Compressor Pressure Relief Valve Inspect area surrounding A/C compressor pressure relief valve for signs of oily residue, indicating relief valve leakage. If oily residue exists, replace relief valve and return to step 1). If oily residue does not exist, inspect refrigerant system for leaks elsewhere and repair as necessary. Recharge system.
6. Check Voltage At A/C Compressor Clutch Coil Check for voltage at A/C compressor clutch coil connector. If 10 volts or greater exists, go to next step. If voltage is not 10 volts or greater, go to step 8_).
7. Check Clutch Coil Ground Connect jumper wire between ground terminal of A/C compressor clutch coil and ground. If clutch engages, repair open in ground wire. If clutch does not engage, replace A/C compressor clutch coil and return to step 1).
8. Check Wide Open Throttle A/C Cutoff Relay Check for voltage at wide open throttle A/C cutoff relay Dark Green/Orange wire. If voltage does not exist, go to next step. If voltage exists, check for voltage at wide open throttle A/C cutoff relay Black/Yellow wire. If voltage exists, repair open Black/Yellow wire. If voltage does not exist, replace relay and retest.
9. Check Fuse Check fuse for continuity. If continuity exists, go to next step. If continuity does not exist, check for short or blown fuse. Repair as necessary.
10. Check Function Switch Circuit Disconnect function switch connector. Turn ignition on. Check voltage at function switch connector White/Purple wire. If voltage is more than 10 volts, go to next step. If voltage is less than 10 volts, check for blown fuse No. 18 (15-amp) or open White/Purple wire. Repair as necessary and return to step 1).
11. Check Function Switch Turn ignition off. Disconnect function switch connector and ensure function switch is in defrost position. Check continuity between Red/Orange wire terminal and Black wire terminal. Check continuity between Purple/White wire terminal and Purple wire terminal. If there is no continuity through function switch, replace function switch. If there is continuity through switch, repair open circuit between function switch and clutch cycling pressure switch. Go to step 1).
I suspect bad pressure switch
Thursday, June 4th, 2009 AT 12:54 AM