A/C Clutch coil

Asked by Jun 14, 2013 at 11:38 PM about the 2004 Toyota Matrix FWD

Question type: Maintenance & Repair

The A/C has quite on my Matrix. The garage says I need a new pump. The pressure is fine. I checked it out myself and the clutch is not engaging. There is power to the clutch 16 volts. I also jumped from the batter to the clutch coil to see if it would engage and it didn't. I have yet to test the ohms at the coil, but assuming that the coil is bad what are the chances that the coil just failed on it's own, or is it more likely a symptom of an over heating pump or something else. I would love to just replace the coil, or even just the clutch, but not to have it fail again. I did find that the coil was not grounded due to corrosion, but I cleaned up the contact to the pump housing, but it didn't fix the coil function.
thanks in advance

8 Answers


If the ground was bad then you could have easily fried the coil but 16 volts is a little high, it should be around 14.2 to 14.7 with the engine running and around 12.5 to 13.7 with the engine off key on. Check the ohms to see if it is open, and check to see if you can turn the compressor by hand, if it turns ok then you can just replace the coil/clutch assembly. Recheck that voltage, it could be an alternator overcharging.

1 of 1 people found this helpful.

The reading of 16 volts was coming out of the harness that attaches to the coil with the engine running. I can turn the pump by hand. Where is the voltage to the coil controlled? thanks so much for your reply.


Measure the voltage at the battery with the engine running, it should not exceed 14.7 volts, if it is over that then something is wrong with the voltage regulator. Make sure you have a good voltmeter that is calibrated properly. Stable voltage is very critical on computer controlled vehicles. So to answer your question about voltage control to the A/C coil it is the voltage regulator for the whole car.

I am getting about 15.46 volts at the battery (car running) and the same at the a/c clutch harness, but I don't know if my meter is calibrated. I get no reading when I check the ohms at the coil. thanks


OK so your A/C clutch coil is no doubt open circuit if you don't get a reading, 15.6 is still a little high, take the RPM's up to 2000 and check the voltage then, write it down, then turn the headlights, take a reading and write it down, with the headlights still on turn on the heater blower on high and take a reading, and write it down then come back here with the results.

So I ran a few voltage checks. I am not getting about 15.29 with everything running (heater,blower,lights) It stays about the same at 2000 rpm. For some reason when I just let the car idle the voltage at the batter would slowly climb, it got up to about 15.49.


So either your voltage regulator is faulty or your volt meter is out of calibration, the voltage is too high. We have a place called battery exchange and they provide free battery and charging systems testing, if you have a place like that there I would have it checked out professionally, if your alternator is actually putting out that much voltage then soon you will start frying components.

thanks so much I will have it checked out.

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