Air compressor cycles when AC is off - AC Cars & Trucks

You most likely have an AC compressor that is cycling on and off to often, this causes the RPMs at idle to fluctuate. The rapid cycling of the AC compressor is caused by a low AC system charge of refrigerant due to a leak in most likely the compressor shaft seal. Please have an AC repair ship confirm this educated guess..

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This most likely is a symptom of low coolant presure. There is a pressure sensor both in the compressor and near the drier / expansion tank on the right side of the radiator. If either one of these senses low pressure the AC compressor clutch is disengaged. The clicking your hearing at idle is probably the compressor clutch cycling. You can watch it cycle by watching the front of the AC compressor pulley. Your watching for the center part to turn when AC is on and not turn when AC is off. Usually this is controlled by a temp sensor but if there is low pressure the preure switches will cause the compressor to cycle. Here is the kicker... you can pay to have the system serviced but.... if they pump it into a vacuum and it won't hold a vacuum there is a pin hole some where in the system usualy the evaporator coils inside the front passenger compartment. No one will re-service the coolant system with a system leak. It is against the law in most states.

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Kelly

YOU COULD HAVE OPEN OR SHORT IN THE BLACK YELLOW WIRE GOING TO AC COMPRESSOR CYCLING PRESSURE SWITCH. CHECK FOR A SHORT OR OPEN IN RED YELLOW WIRES AT THE AC PRESSURE CUTOFF SWITCH. USE VOLT METER AND CHECK FOR VOLTAGE AT BOTH SWITCHES. PROBLEM COULD BE IN THE EATC MODULE THAT SEND POWER TO PURPLE WIRE THAT FEEDS THE AC PRESSURE CUTOFF SWITCH AND AC CLUTCH CYCLING PRESSURE SWITCH THEN FEEDS THE AC COMPRESSOR CLUTCH SOLENOID.

I would check the following possibilities:
1. Is compressor clutch working? - You need to do this when the ac is blowing hot air only - locate compressor drive pulley on engine - rubber belt wraps around it. Start engine and set to max ac. When the ac is blowing hot air, look at the center of the compressor drive pulley using a good flash light - watch it for a while, it should be spinning with the pulley - this means the compressor is engaged. If not, the compressor is not engaged. If your ac is blowing hot air, then the compressor should be engaged and running (trying to cool). If it is not engaged, then your compressor clutch is probably going out. Could be low voltage to clutch, but more likely the clutch is worn out and only working some of the time. Note: if working normally, the compressor clutch will engage and disengage in cycles- but the air should always be cold. If clutch is bad, compressor would need to be replaced (sold as one unit). This is tricky to diagnose and could take some time - you need to do it when ac is blowing hot air but set to max cooling.

2. Low on refrigerant or refrigerant has moisture in it? If your ac blows cold initially after being off for a while, then heats up, and continues to regularly cycle back and forth between hot and cool air, then the system may be low on refrigerant or the refrigerant may have moisture in it that is freezing and restricting refrigerant flow. An a/c shop can check refrigerant level and even replace refrigerant if moisture is suspected.

Could be other issues, but I would start with these.

Good luck

**** in the venturi valve ,remove the ac interior unit and clean it all out ,broken bits of the old compressor blocking the restrictor (venturi )

yes it keeps the humity out of the air in you car

CYCLING COMPRESSOR COULD MEAN TOO MUCH OR TOO LITTLE FREON.TAKE IT TO AN A/C SHOP

when you use the front defrost in the winter the cycling of tha a/c compressor will cause this condition.

when you use defrost the a/c is run to de-humidfy the air that is blown onto your windshield.


in the summer this is not a big deal as it is hot enough outside to keep the a/c system pressure above the compressor clutch cycle threshold. but in the winter the general lack of heat in the ambient air and the lack of humidity results in rapid cycling of the ac compressor.

the idle is bumped up to compensate for the load of the a/c compressor, or else your engine would stall out. but when the compressor is disengaged the idle is dropped. but it raises again when the compressor cycles back on.

there may be a good chance that your ac is under charged after all these years. when the weather gets warmer have the charge level in your ac system checked.

a low charge will also increase the on off on off cycling of the ac compressor, usually resulting in the complaint that you have. so the base issue of your problem is low ac system charge.

have you checked the compressor oil it may be seizing up