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My GTM is a couple years out of completion and I have had some AC issues for which I'm worried my compressor is out. When the car was done I had the AC system charged. It worked great for the summer. It was stored over winter and the next spring the AC was out. The pressure readings were low. I put it under vacuum and it didn't leak. I wondered whether the Schrader valve for the low pressure line had a slow leak since when it was first charged the guy who charged it up questioned that. I put a new one in and recharged the system.

It worked great all last summer. It was stored during the winter again. When I took it out this spring the AC again was out. The pressures were low again but not zero. I tried to charge it again but now it looks like the compressor is out. The clutch engages and I can see it spinning but it doesn't put any strain on the engine at all when it engages. The high and low pressure ports both measure 50 psi and it doesn't change when the compressor engages. When I drive there is a definite difference in air temp coming out of the vents when the AC is on versus off so it seems that something is circulating but not enough to cause any pressure change, which makes me wonder how any cool air comes out at all.

Its a new LS3 with a new AC compressor. I put the required amount of PAG oil in the system. I even installed an RPM window switch to make sure I didn't have the compressor running over 4K RPMs. I have a couple of questions:

1. Is there anything else that could be acting this way other than a blown compressor?
2. If a blown compressor is the only thing that this could be how could it have happened, since it had oil in the system and it never runs past 4000 RPMs?
3. What is involved in replacing an AC compressor on a completed GTM? Does the body have to come off?
4. Does anyone want a GREAT deal on an essentially new GTM (1000 miles) with marginal AC?!
 

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There is only one possibility I can think of that would cause the conditions you're talking about. If there is a definite difference in air temp out the vents with compressor on vs off, but the pressure doesn't change between high and low side.....the only thing I can think of that might cause this is that your orifice tube blew out of place. So you still have refrigerant circulating thru the system....but you don't have the pressure drop thru the orifice that's required to lower the temp of the refrigerant in the evaporator core. Unfortunately, on a finished car, that might actually be way worse than having the compressor go out.....since the extension tube that the orifice installs into is all but impossible to remove from the AC unit without tearing things apart in the tunnel.
 
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