apd628

I bought the car this past Winter, or at least what passes for Winter here in Texas. When I got the car, a lot of things did not work, and the last major issue is the AC. Since the temps are in the 100 degree range, I thought it would be a good idea to have a go at the factory AC.

I put my gauges on the system, then set the vacuum pump to work. I let it run for 45 minutes to be sure I evacuated the system, I let it sit for 20 minutes to see if the vacuum would hold, and it did. I then started adding r134a to the system, it had been updated by a prior owner a few generations back.

As the system pressures started to approache the numbers on the high and low side which would cause the clutch to start cycling, it did not. I thought my low pressure sensor cut off switch was not working right so I ran 12 volts to the driver side of the two prong plug on the compressor, and the clutch started working fine, and I filled the system to spec. as per the Chevy shop manual.
The car cooled down quite nicely, as it was blowing 46 degrees out of the vents, not too shabby since my shop temp was 95. The car has a nice auxiliary fan, and I had a couple of extra fans blowing into the intake of the radiator.

The next day I went to the parts store, and got a new low pressure cut off switch. I installed it, and fired up the system. The compressor immediately started clicking on and off quite rapidly, and I was back to blowing hot air again.

From the car, not me.

System is still pressurized to shop manual spec.

Any ideas?



Thanks

rebel542

I think when you ran 12+ to the compressor clutch you bypassed the entire electrical A/C control system. Just a thought. You may have wiring problems elsewhere. Oh yea, check fuses.

kenmohr

Having same problem all ears

Jud Chapin

How did you determine the pressures were ok with the comp. cycling on and off? I'm wondering if the system has a leak. I assume it was empty when you started working on it as you mentioned vacuuming it out immediately with no reference to refrigerant evacuation. Did the gauges show zero pressure at first? Another factor is just because the system held vacuum after pump down is not 100% proof the system is leak free.

What I would do next is leak test the system with an electronic leak detector. Be sure to get the sensor all the way down into the evaporator casing (both sides) and check the bottom of the casing for oil which would be a sign of the evap. is leaking. Also be certain the hoses are in good shape with no oil residue on them.