My dad got one of those Autozone charge kits. With A/C running…Checked the pressure at first, it was at 0. Added some, got to about 20psi it kicked on, then dropped, kicked on, then dropped. It’s in some sort of cycle now and I’m afraid to add more.
Any suggestions? :embarass:
Car A/C systems are a real pain.
The systems that I have worked on (and it sounds like yours works the same), have two “inputs” for the compressor to run. The first “input” is the selector switch on the dash - e.g. turn on the A/C. The second “input” is a differential pressure switch. The differential pressure switch checks the high side and low side pressure of the compressor and if the difference in pressure isn’t high enough, it “turns off” the “input” and the compressor won’t run. This is a self-protection mechanism to reduce damage when the system is low on refridgerant. The pressure cycling the you are seeing is likely the differential pressure switch deciding to shut off the compressor.
At this point, I don’t recommend running the system until you find your leak. Once you find the leak, you can decide what the next course of action should be.
These systems are rarely easy or cheap to fix. Trust me - I’ve have a few systems go bad for various reasons.
Let me know what you find, I might be able to give some advice…
My neon has always done this…it was out of coolant for a while and wouldn’t get cold…got a refill thing from kmart…filled it without a gauge(dumb) and it is cold as hell now, my ac pump has always seemed to “breathe” on-off-on-off
If the pressure in the system gets too high/low it will cut out the compressor.
Don’t see a leak. Am I ok to disconnect the sensor at the compressor? It must be reading proper psi on low side where I filled it vs. nothing on the high side (assuming) since there was no pressure in the system and the safety turns off the compressor before the freon has a chance to circulate thru.
That doesn’t mean its working properly. I knew immediately that the cycling sound wasn’t right.
I think the pressure is indifferent rather than too high right now.
If you’ve chased down the lines to the accumulator, evaporator, condensor and compressor and nothing looks wet then it’s hard to say where the R134a is going. Doing this is indeed a PITA.
***If this were my car and I weren’t using the system because I was worried about it *** I would simply add more refridgerant in smallish increments and see what the system pressure is and observe the behavior of the compressor as I added more. You can overfill these systems but it has been my experience that with those little cans, it’s hard to do.
Another potential reason that you are seeing the cycling is that the internal parts of the compressor are worn and the piston can no longer hold pressure when compressing the refridgerant. This is an expensive fix involving replacing the compressor, orifice tube, accumulator, a system purge with a vaccuum and then a full, new fill of R134a… Just thinking out loud.
it sounds like it is still undercharged