No rear AC just blowing hot air

[MattGiggz]

Hello all, new here to the forum. Just recently bought a 2004 GMC Yukon Denali AWD. Truck is great, only thing issue I have is the AC doesn’t work in the rear. Is this a big fix/expensive to get repaired? Thanks

 

[OR VietVet]

Welcome to the forum.

So, the front a/c works as hoped, correct? Does it make a difference if you are on AUTO or MANUAL operation? Have you had gauges hooked up to the system and if so, can you give readings? I am also assuming that since you just bought the truck, you knew about this problem when you bought it and if so, what did the original owner say about it and did he/she make any repair attempts and again, if so, did you see paperwork? was there any previous a/c work paperwork supplied?

 

[UmmScott]

Your post says just blows hot air.
First I would confirm that the blend door for the rear ac works.
Switch it from full cold to full hot and you'll hear a difference and if the engine is at operating temp then you'll feel the difference too.

If that checks out ok then its an issue with the AC system, likely a failed expansion valve. But, even before that....
Are the hoses to the rear system hooked up? Believe it or not some people will abandon the rear AC and heat. I've seen that .
Open the hood, if you see the refrigeration lines tee'd right after the accumulator then theyre connected.

If everything is connected and looks ok and the front AC is ice cold then you likely have a failed or plugged expansion valve for the rear evaporator coil