The AC on my '92 has never gotten very cold since day one. It has always cycled on and off every 5 seconds or so. Last year an AC shop told me this is not normal. They said it was because the seals were all bad and I was low on freon. But it has done this since new, so I am thinking there is a defective part of some kind, either a bad relay, sensor, or thermostat. Anyone know what causes this cycling?

 

Usually that means you are low on freon. I know on my '88 mustang there is an a/c relay that controls the clutch that has gone bad once, but it turned the a/c clutch off instead. The relay on the mustang is connected to the low pressure switch and also turns the a/c off under WOT. Get a pressure gauge at an autopart store and check the pressure. If low then it is time to refill the freon.

edit: re-read your post and saw you said it has done it since new. Could be it was low on freon when new and you don't have any leaks so it has just been that way too. Check to pressure to rule that one out.

 

If your not getting cold air you need to check the pressure in the system and check for refrigerent leaks. It is normal for the compressor clutch to cycle on and off to regulate the pressure in the system. The only compressors that don't kick on and off are the variable displacement type compressors but in the early 90's i think GM was the only ones using them.

-Jon

 

My 97 F-150 has an air conditioning compressor cycling switch mounted by the receiver/dryer at the firewall. Had to replace mine because the compressor would cycle constantly. The switch is similar in style to the low pressure switch.
Good Luck

 

I bought the cycling switch yesterday. It's cheap enough to try. If that's not it I'll take it to the AC shop. Thanks for all the replies.

 

Thanks for posting this question laneman. I needed to ask the same thing, my 86 F-150 cycles constantly (every 5 seconds or less) and I just refilled mine with FREON? So I know I'm not low on coolant.

Let me know if this works? Thanks

Sorry I highjacked your post

 

I haven't installed the switch yet, but I did learn that they are adjustable. Yesterday I turned the screw out 1/2 turn and gained a 3 second increase in time. The screw is located inside the switch after removing the plug. I'd like to find out what the times should be. Mine was at 7 seconds on/8 seconds off. Now it is at 10 seconds on 10 off. The air is no colder though, so I think I have a slow leak. I had it recharged about three years ago, but it's getting warmer again. If you do buy the switch be sure to ask for the o-ring that is sold separately. Coat the o-ring with a small amount of mineral oil. The plastic base switch screws in hand tight only. The switch can be installed without removing the freon, but some will escape while changing them.

 

Thanks for the help My main problem is I can actually feel the pressure releasing under my floor board about ever 3-4 seconds (which you can feel, my truck actually feels as if someone taps the brakes each time the pressure releases)

Thanks again and good luck