Generation Specific => Second Generation 1970-1981 => Topic started by: jbanna on July 14, 2023, 03:38:47 PM
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Hello experts - my 78 a/c compressor is not cycling on, and the pressure (134a freon) seems ok; I troubleshot the wires to the unit, with no visible breaks, and the fuse at the box is intact as well...any suggestions? I hope the compressor didn't die...
Thanks,
Joe
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When you say you were troubleshooting the wires did you test for 12v? There are a couple of switches between the power source and the compressor. One is a thermal switch meant to open the circuit if the evaporator core freezes. The other is the low pressure switch meant to open the circuit if pressure is too low. How did you verify your refrigerant is full?
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If it's not cycling, as in clutch isn't activating, it isn't getting power to it. That can be due to many potential issues that involve wiring issues or pressure switch, as well as low content pressure.
When you turn the AC on, is the compressor clutch activating and spinning with pulley? Otherwise, if you unplug the pressure switch on the drier and add a jumper wire across both terminals it bypasses the switch and will let you test if there's power getting through to the compressor. If so, this only tells you one of two things, you have a faulty pressure switch, or the pressure is so low that it is operating correctly. Remove jumper wire after testing, not for AC use.
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Thanks for the help!
The pressure switch is ok, but I did find my thermal switch copper probe was broken, so I ordered a replacement; hopefully that is the only problem...I checked the low pressure port
with an a/c pressure tester, even though the clutch was not cycling, I think it still gives me a good idea of the freon level...
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That'll do it too. The improved switches with a low and high pressure point saw the probe no longer needed. The good ones could also be adjusted.