New compressor less than two years old and was working great. car was idling in stuck traffic with ac on and it started blowing hot air. Looked at ac clutch and its not engaging. Car has since been used and doesn't overheat.
Here are the test performed to diagnose ac clutch not engaging.
key off engine off:
1) checked freon on the low side. pressure looks within good range for the ambient termperature.
2) disconnected connector at clutch. set voltmeter to continuity setting, connected red lead to ground terminal on the harness side and black lead on compressor body. Voltmeter generated tone. Concluding coil and ground circuit are good.
3) checked resistance between the two pins on the ac compressor where harness connects. got 3 ohms with volt meter set to 2K ohms setting. concluding compressor coil is good.
key on engine off, blower on:
1) checked ac fuses in the passenger and engine compartment fuse boxes, all good.
2) pressed ac switch , ac light comes on, ac relay doesn't click. Replaced relay with known good, still doesn't click. bench tested relay and it clicks.
3) checked voltage at clutch connector harness side positive terminal. no voltage
4) removed relay and checked for 12V at relay terminals 30 and 86
5) jumped relay terminals 30 and 87. Getting 12 V at the clutch connector harness side positive terminal.
6) radiator fan also doesn't come on. bench tested both high speed and low speed relays and they are fine. have power at relay terminals 30 and 86.
7) tested ac low pressure switch and its good.
engine running
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1) blower at max, ac switch pressed, light comes on.
2) rpm rises when ac switch is pressed, ac light comes on
3) fan comes on after a some seconds.
4) also jumped ac low pressure switch. clutch still did not engage
Here are the test performed to diagnose ac clutch not engaging.
key off engine off:
1) checked freon on the low side. pressure looks within good range for the ambient termperature.
2) disconnected connector at clutch. set voltmeter to continuity setting, connected red lead to ground terminal on the harness side and black lead on compressor body. Voltmeter generated tone. Concluding coil and ground circuit are good.
3) checked resistance between the two pins on the ac compressor where harness connects. got 3 ohms with volt meter set to 2K ohms setting. concluding compressor coil is good.
key on engine off, blower on:
1) checked ac fuses in the passenger and engine compartment fuse boxes, all good.
2) pressed ac switch , ac light comes on, ac relay doesn't click. Replaced relay with known good, still doesn't click. bench tested relay and it clicks.
3) checked voltage at clutch connector harness side positive terminal. no voltage
4) removed relay and checked for 12V at relay terminals 30 and 86
5) jumped relay terminals 30 and 87. Getting 12 V at the clutch connector harness side positive terminal.
6) radiator fan also doesn't come on. bench tested both high speed and low speed relays and they are fine. have power at relay terminals 30 and 86.
7) tested ac low pressure switch and its good.
engine running
--------------
1) blower at max, ac switch pressed, light comes on.
2) rpm rises when ac switch is pressed, ac light comes on
3) fan comes on after a some seconds.
4) also jumped ac low pressure switch. clutch still did not engage
May 25, 2026 at 6:15 PM
