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Joe Marconi

Pulsing Voltage To A/C Compressor, 02 VW Jetta

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A 2002 VW Jetta arrived at our shop the other day, the customer complaint…no air conditioning. The system was fully charged so we started our diagnostic tests and found that there was a pulsing voltage to the a/c clutch. The fan control module would pulse a 12 volt signal every few seconds.


After a little research we learned that a faulty compressor clutch could be the fault. We ohmed the clutch coil and found it open. We replaced the compressor clutch and now the FCM sends a constant 12 volt signal and all is ok.


Maybe others have seen this, but it stumped me and my lead tech at first. Apparently, if there is a problem with the clutch coil, the voltage will pulse from the FCM.


It’s a good thing we did a little research to find how the system works before shot-gunning the problem.

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