AC compressor wont kick off.

[lance_covel]

I have a 1986 Chevy z28. Had some AC work done a few years ago. When I went to use the ac this summer I found out that my compressor was not shutting off. The only way to shut it off is to turn off the AC from inside the car, shut the car off, or manually disconect power from the compressor itself. Has anyone else had this problem, or know the solution?. Thanks.

[89IROC&RS]

um, if the engine is running, the compressor has power, and you have it turned on, its supposed to keep working.

[lance_covel]

Originally Posted by 89IROC&RS

um, if the engine is running, the compressor has power, and you have it turned on, its supposed to keep working.

What I mean is that the compressor does not cycle off and on. This condition persists in the normal and max AC setting. I know that it is supposed to shut off and on, at least thats the way it worked two years ago. By the way, the red Camaro looks just like mine minus the T's.

[89IROC&RS]

the ac compressor is not supposed to cycle on and off. that is caused by a low refridgerant level which causes the pressure switch to register high and low pressure causing the compressor to cycle on and off. i would say that you were low on refridgerant before the AC work and now it is operating as designed.

[Hypsi87]

Originally Posted by 89IROC&RS

the ac compressor is not supposed to cycle on and off. that is caused by a low refridgerant level which causes the pressure switch to register high and low pressure causing the compressor to cycle on and off. i would say that you were low on refridgerant before the AC work and now it is operating as designed.

accually they are supposed to. Since GM uses a fixed orface tube, they cannot regulate pressure like you can with an expansion valve system. So they have a high pressure switch and a low pressure switch. when the compressor pressurizes the r-134a, to the max pressure, it turns the compressor off and lets the pressure equalize, then when the pressure dropes it will kick the compressor back on.

it should not do it at idle but at RPM, it will do this. if your compressor is doing this at idle, it is usually a sign of overcharge

[89IROC&RS]

well, i cant say as ive ever worked on an AC system while the car was doin 55mph down the highway, so im saying its not supposed to cycle because the car would normally be at idle while you were working on it. and therefore not turning on and off.

[Hypsi87]

Originally Posted by 89IROC&RS

well, i cant say as ive ever worked on an AC system while the car was doin 55mph down the highway, so im saying its not supposed to cycle because the car would normally be at idle while you were working on it. and therefore not turning on and off.

LOL that would be crazy tryin to read gauges at 55

just kick the RPM up to around 2500- 3000 RPM. it will do it.


I think your supposed to check your pressures at like 1500 RPM or something like that anyway.

[89IROC&RS]

i think trying to keep the cart upright while its being dragged alongside the car would be the hardest part lol.

but anyway, ive never checked line pressures with the engine running. we evacuated the system and checked the actual ammount of refridgerant that was in there and went from that. the machine had the ability to check line pressure, i just didnt do it, my way was easier, and IMO safer.

[Hypsi87]

Originally Posted by 89IROC&RS

i think trying to keep the cart upright while its being dragged alongside the car would be the hardest part lol.

but anyway, ive never checked line pressures with the engine running. we evacuated the system and checked the actual ammount of refridgerant that was in there and went from that. the machine had the ability to check line pressure, i just didnt do it, my way was easier, and IMO safer.

if you don't run the car, how can you tell the high side and low side. if the compressor is not running, then the pressures are equal.

[89IROC&RS]

learned the system, kinda like recognizing the intake and exhaust of the engine. not to mention that the ports on the high and low pressure sides are different sizes. i dont remember which way it is right now. but i think the blue hose had a bigger port, and the red hose had a smaller port. and again i could be backwards but i think high side was the blue hose and red was the low side.

[Hypsi87]

Originally Posted by 89IROC&RS

learned the system, kinda like recognizing the intake and exhaust of the engine. not to mention that the ports on the high and low pressure sides are different sizes. i dont remember which way it is right now. but i think the blue hose had a bigger port, and the red hose had a smaller port. and again i could be backwards but i think high side was the blue hose and red was the low side.

no I am talking about the highside pressure and the low side pressure not what connectors they use. If the compressor is not running, then how do you read the pressures? With the compressor off, your low side pressure should be equal with your highside pressure. Then when you kick on the compressor, the r-134a before the orface tube will be somewhere in the 115-145 PSI range and the r-134a on the other side of the orface tube will be 45-60 PSI range.

If you check your pressures without the car running how can you check your pressures

[89IROC&RS]

oh, i didnt, thats what im sayin, id evacuate the system and pull a vacuum to check for leaks, and then recharge the system. most of my diagnosis problems were pretty easily solved. i may have checked line pressures with the engine running, i just dont remember doing it. i understand the high side low side due to the compressor and the oriface tube, i just never really ran into it.