Suburban A/C (front/rear different temp)

[scottydl]

Lately the A/C in my Suburban has been a little finicky. Last month during a camping trip (while towing my 9k# trailer) the A/C was pumping along cold, working just fine. Then it quit blowing cold air at all, output turned musty and warm as if the compressor shut off completely. I had just topped off the R134a the previous day, and it wasn't all that low anyway per pressure gauge. (62 degrees at the front vents then.) I first thought something broke completely, but then awhile later the A/C got cold again and was fine the rest of the trip.

No more problems until a few days ago, and I noticed the front vent air seemed a little damp and not as cold... but the rear vent air felt fine. Got home and measured front vent temp at 68 degrees, rear at 62 degrees. Then today all vents felt fine again while driving, especially when the Recycled Air mode kicked on.

If R134a is leaking somewhere, I would think the rear air would lose coldness before front... but the opposite is happening. And the air would steadily get warmer and stay there, not this switching back and forth. This system only has one compressor, right? But two condensors and fans, one front set and one rear set. What should I be looking at?

 

[bugdewde]

Hmmm...... Not an A/C guy, but if the front is warmer than the rear, and the refrigerant is all one loop, I'd suspect the condensor or fan for the front..... Or maybe a component in the front condensor? Not really sure what components are seperate front/rear. Orifice, dryer, etc.???

So, first and easiest check might be to see if the front condensor fan is working when this happens again.

 

[tahoe.mkIII]

The front ac uses an orifice to create the pressure differential and the rear uses a thermal expansion valve. They work differently but do the same thing, usually the txv in the rear gets stuck/clogged first as they are more finicky. If something is partially obstructing the orifice in the front loop it can freeze up which will change the pressure drop and can ice up the front coil. The orifice has a screen on it than can get gummed up as well(if leak seal was ever put in there, or if your compressor is going and sending debris into your system).