front a/c cold; rear a/c hot

My front air conditioning is blowing cold air just fine, but my rear unit is blowing hot. All the controls are set to cold for the rear and the blower is operatiing fine. I know there is a separate evaporator, but is there a separate R-134 loop? Could the rear be low R134 without the front also being low? What else could it be?

BTW, about two weeks ago I lost my a/c belt. It completely disappeared somewhere....but the compressor spins fine and the clutch operates normally.

Thanks in advance for your inputs...

Take a look at http://www.automotiveforums.com/vbulletin/showthread.php?t=433145

//2000CAYukon

Thanks for the reply 2000CAYukon....Both lines at the back evaporator are warm when I fully load the a/c on max, one is just a bit warmer than the other; unlike the front where the one line is so hot you can't touch it. The low pressure side at the accumulator is reading 54 psig.

This is a 2002 Yukon.

I cannot find the rear orifice tube.

I traced all the way back from the rear evaporator connections to the compressor. There is what appears to be an aluminum manifold at the compressor where the lines tee off.

Is there a fixed orifice plate at the evaporator? Is there only one orifice tube on this model and something else is wrong? (I tend to agree with you and thinkits a second orifice tube too.)

Also, if the second orifice is plugged, what could have plugged it? The last time I had to replace an orifice, my compressor failed and put crud in the lines. Could my compressor be failing and that's why I threw a belt, even though it spins nicely now and provides cold air up front?

Thanks for the reply 2000CAYukon....Both lines at the back evaporator are warm when I fully load the a/c on max, one is just a bit warmer than the other; unlike the front where the one line is so hot you can't touch it. The low pressure side at the accumulator is reading 54 psig.

This is a 2002 Yukon.

I cannot find the rear orifice tube.

I traced all the way back from the rear evaporator connections to the compressor. There is what appears to be an aluminum manifold at the compressor where the lines tee off.

Is there a fixed orifice plate at the evaporator? Is there only one orifice tube on this model and something else is wrong? (I tend to agree with you and thinkits a second orifice tube too.)

Also, if the second orifice is plugged, what could have plugged it? The last time I had to replace an orifice, my compressor failed and put crud in the lines. Could my compressor be failing and that's why I threw a belt, even though it spins nicely now and provides cold air up front?

The orifice tube is inside one of the rear lines. Hard to say what clogged it but first thing to to take a look at it and see if it is your problem. Otherwise, the evaporator may be bad.

//2000CAYukon

From what I've gathered, it could be worse than I initially thought. Evidently the reason I lost my a/c belt was that the compressors froze up momentarily. (Based on what folks are beginning to tell me.) The reason my rear expansion valve got plugged is most likely due to bits of compressor bearings making their way through the system. It doesn't sound different to me, but I haven't gotten close enough to listen to it over the engine noise. Right now I'm preparing to replace the compressor, orifice tube in front and expansion valve in back (accumulator too) for a pricey job I wish wasn't needed on an '02 vehicle.

From what I've gathered, it could be worse than I initially thought. Evidently the reason I lost my a/c belt was that the compressors froze up momentarily. (Based on what folks are beginning to tell me.) The reason my rear expansion valve got plugged is most likely due to bits of compressor bearings making their way through the system. It doesn't sound different to me, but I haven't gotten close enough to listen to it over the engine noise. Right now I'm preparing to replace the compressor, orifice tube in front and expansion valve in back (accumulator too) for a pricey job I wish wasn't needed on an '02 vehicle.

Going through the same thing. Front AC ok...but rear is hot. I'm noticing a "ratcheting" noise coming from the COmpressor when I first start out driving. If you replaced everything above, could you give me the price so I can shop around. Thanks

I ended up having to have the orifice tube, compressor, accumulator, and expansion valve changed. I was going to do it myself for about $600, but GM did a goodwill repair for me. The prices I was quoted before they offered the goodwill repair ran from $800 from a private shop to $1200 from a dealership. The dealership gave a lifetime warranty on the compressor (if they are Goodwrench certified), which I figured if these things go this soon, chances are I'll need another. If yours vehicle is realtively new, ask the dealership about how to get a goodwill repair done, where GM helps offset some of the cost. Good luck!