2005 Yukon XL Denali A/C issues… Help?

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BigOleFishStix

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Hey all, first time posting here. So if this has been discussed, forgive me and maybe point me in the right direction.

I have an 05 Yukon XL Denali. The A/C system has gone strange. I’ve only owned it for a year or so. Now that summer is here I need A/C and don’t have it.

Here’s the facts. Inside the rig the vents don’t change. So it just blows everywhere in a sense but mainly floor and defrost vents. Nothing will change this. I also can’t get it to stop blowing blazing hot on the passenger side. The air won’t even kick on. Compressor wont kick on. I took the blend door actuator out of the passenger side to see if it was broken inside or if I could be fixed. That’s as far as I’ve gotten. I’ve also done the “reset” with pulling fuses and ignition etc..

I’ve checked the hvac fuses and relays. All good. I was hoping to fix this on my own before taking it to a shop. So hoping we can come to a conclusion. Any help is appreciated!
 

OR VietVet

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Welcome to the forum.

Are you saying it only blows hot on the passenger side but blows cold elsewhere or that it does nothing but blow hot everywhere? You need gauges on the system to see what static pressure is, if the compressor clutch is not kicking in, or if is kicking in/on, then what are the pressures then? Basics first.
 

Doubeleive

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first you should probably address the ac pump not working, the rest is easy stuff
this would involve verifying if the pump is any good and if the system has pressure to make it work.
unless you have the tools needed to check it then you should probably seek out a "free inspection" that many shops offer in order to drum up business. that will at least give you a starting point.
 

OR VietVet

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If you do as @Doubeleive suggested and take to a shop for free inspection, or even a "pay" inspection, get complete documentation of what they say is wrong. A service person just saying "your a/c system is bad", is not a diagnosis.
 

Scott in AZ

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Sounds like the AC vent door actuators under the driver side dash (floor/defroster dash/front dash) are failed so you are only flowing thru the top defroster and blow by in the bottom; and a failed HVAC compressor (hot air) or failed mixer (hot/cold) vent actuator.

The hot/cold mixer actuator on the passenger side is easy to get to. The vent door actuator is very hard to get to, but it’s possible for a patient novice with tools. I have a thread on replacing the vent door actuator that restored air flow thru my front dash when it was stuck on the defroster upper dash station.

This is a very common problem in 15 to 20 year old GMT800’s.
 

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ScottyBoy

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Great Scotts think alike. I was just about to say that there's definitely a few bad AC actuators. The mode actuator for sure, and the passenger side blend actuator. Possibly driver side blend as well.
 

rockola1971

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Vent problems sound totally separate of the No A/C problem. The compressor clutch will not engage if the refrigerant pressure is below around 20psi. This is a safety feature to protect the compressor from spinning with no refrigerant/oill mixture in the system because of a leak. The low pressure cutoff switch is the actual electrical safety. More often then not the leak happens at the low or high pressure schrader valve port. (where you read pressures and charge the system). Usually its the low side schrader valve. They will become loose when someone sticks a gauge hose on it and the hose weight causes the adapter to turn and thereby backing out the schrader valve on the low side causing a leak. Sometimes its a big leak and sometimes its small that takes all winter to get low enough to engage the low pressure cutoff switch. ALWAYS SNUG SCHRADER VALVES AFTER SERVICE. Its free insurance. Then of course there can be leaks at the compressor, evaporator(s) and even the condenser can catch road debris and get a puncture. A good shop will find the leak and fix it if you desire. A leaking evaporator(front) can get very expensive in labor because the whole dash has to come out. Get that wallet out!
 

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