Another A/C question

[Scott R]

I recharged my system AGAIN on Friday with R12 and it's holding a good charge, 150 high and 35 low, and the compressor is coming on. But it's cycling on and off about every 20 or so seconds.

So in my thinking I have either a bad pressure switch, or a bad climate sampling unit. But I am not sure if the climate sampling unit could cause this sort of problem.

Any ideas?

[Lawrence Coppari]

Is it really a problem? What is the outside temperature when it does this?

I have one car that uses F12. In cool weather it cycles on and off frequently- 30 seconds. When hot, it remains on a lot longer.

I was on a long drive yesterday in my sedan that uses 134. Temperature was coolish. It cycled on and off.

[Lawrence Coppari]

And to add one more comment....A colleague of mine here in the office just bought a used car, a 1998 Buick. The AC did not work. He took it to the repair place and was told that GM designed the system in those years so that it remained on continuously. The compressors are all failing at 30-50K miles. The new compressor that was installed operates the same way - runs all the time. The AC tech said he should shut it off every 1/2 hour when on a long drive to lengthen its life.

Maybe it's good that your system cycles.

[Eric 951]

Scott,

I just got my compressor wiring re-attached this past Friday, and once I engaged the system, it cycled about every 45 seconds or so--cabin cooled as I expected it--so maybe this is an inherent condition?

[Lawrence Coppari]

Eric,

It's good you got it working.

[Scott R]

Maybe it is, but I swear that it used to remain on almost all of the time in the past.

One thought I have is that I did not vac all of the moisture out of the system and it's freezing near the temp cutoff switch, and when kit thaws it starts again.

Or that I may have my high side pressure too high, or a faulty pressure relief switch. My vent temps seem a bit high at 50deg. So I may evac it this weekend and vac it down again, and test that pressure switch.

[Eric 951]

Lawrence,

Thanks. The two wires ended up connecting to each other - Oh, well, it was better to be safe than sorry.


Now the cabin is nice and cool again.