A/C compressor never shuts off

[AtlantaDan]

Previous owner installed all new A/C components, but something isn't right because the compressor (York) never shuts off or cycles. If it's plugged in via the low pressure switch - it's running. Even with the system off. Any ideas where I should start troubleshooting?

[Srdayflyer]

if the pressure sw. is disconnected the compressor should not run,period, were the a/c components replaced the same a factory ? , i would also check the on off/temp control sw. for proper operation , the switch may be broken internally and be on internally again with the L.P. disconnected it should not run, there should be only 2 wires going to the compressor, and the only thing those operate is the compressor clutch to energize the magnets to engage the fan belts, ground and power from the freon low pressure switch, the switch protects the compressor from running when no freon is in the system

[will e]

Are you familiar with circuit and the use of a multimeter?

[AtlantaDan]

@srdayflyer - if the pressure switch is disconnected the compressor stops running. That's the only way I have found to turn it off. I'll start poking around under the dash. I was wondering if the thermistor has anything to do with this problem - does an 89 AC system have one of those?

@Will - Yes, I am familiar with a DVM and circuits.

Thanks!

[Srdayflyer]

the thermistor is buried up in the air plenum box i would 1st just check the a/c fan clutch and make sure it engages properly, 2 wire 1 is 12v the other is ground clutch should engage and disengage when power is applied or removed but you really need a factory manual and or access to the wiring diagrams (tom ol collins jeep) web site should have the wiring dia's, these are simple rigs to work on , but their a fully hands on owner repair type trucks, help is here and specialty 4x4 shops may or may not be able to help not very many old school guys left out there, it scares the living hell out of so called mechanics there days if they 1 cant plug it into a diagnostic computer, 2 open the hood to find the motor, there's so much crap in there would take them 2-3 shop hours just to find the motor. just m.o. but rest assured you will get your answers here or on previous blog'd questions

[Stuka]

There should also be an override so that if you have the AC turned off in the cab, it disconnects the clutch so that the compressor isn't engaged.

[will e]

@srdayflyer - if the pressure switch is disconnected the compressor stops running. That's the only way I have found to turn it off. I'll start poking around under the dash. I was wondering if the thermistor has anything to do with this problem - does an 89 AC system have one of those?

@Will - Yes, I am familiar with a DVM and circuits.

Thanks!

Great! That will help.
So if the pressure switch is connected the compressor always turns on. Regardless of any other control settings?

If that's the case trace the wire from the switch to its next location or power source.
Curious. Does the compressor clutch engage even with the ignition turned off?

[seventynine]

Something is not right here. You say it’s a York compressor? They were using Sanden compressors starting in ‘89. York compressors don’t have low pressure switches. They are oiled via their own internal crankcase oil supply. The will turn on with or without Freon in them….which is why they make great onboard air compressors

It must be a Sanden right?