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GMC System Freezing Up (long read)

Bonedog on Mon April 28, 2008 2:56 PM User is offline

Year: 2001
Make: GMC
Model: Yukon

This will be a bit long so I can truly describe everything that's gone into creating, diagnosing and trying to remedy this situation.

Last spring my compressor was replaced with a new GM unit by the dealer. They mentioned they had to flush the system numerous times because of how much of the compressor was running through it.

Fast forward to the summer when I started experiencing similar problems as others who've posted here. Only after driving the car for an hour or more, the amount of air out of the dash would decrease even though the blower motor was at a consistent speed. The air that WAS coming out was cold but not much volume. I mentioned that there was an ENORMOUS amount of water draining below the hood. The dealer replaced the actuator door and said it was fixed.

Not too much later, the problem resurfaced and I lost confidence in the dealer's ability to diagnose. I took it to 3 different shops and came back with puzzled looks from each of them. It happened again so I took it to the dealer and told me it was due to the thermostat on the dash being non-responsive and charged me an arm and a leg to replace that switch.

Several weeks ago I had been on the road and had the same situation come up so I drove it to the dealership with the problem present. They ran the scanner and couldn't find anything wrong so I told them to open the hood. There we found the accumulator and low side hose with 1/4" of ice on it. The high side which should have been hot to the touch is actually cold. We turned the heat on and defrosted the system and turned the AC back on and it functioned normally.

We replaced the cycle switch thinking it wasn't functioning correctly and I went on my merry way. Since, I've opened the hood on any drive I take to see if it's freezing up. Well, it is.

Since the high side's not hot, (and I'm not equipped to work on AC's), I'm looking for ideas on what the culprit is so I can tell the shop what to do rather than the other way around. I've been told it's either a clogged orifice tube or too little refrigerant. Anybody care to diagnose?


mk378 on Mon April 28, 2008 3:32 PM User is offline

The cycling switch keeps things from getting too cold. Make sure it's really cycling off. With a gauge manifold you can measure the pressures and that will tell a lot. If it's a 2 wire switch, you can test by unplugging the switch. The compressor should always stop when the switch is unplugged. Maybe a relay gets stuck or something.

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