Rear A/C blows room temp

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Tyler Gober

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Ok... First off im sorry if this is the wrong section for this.....so I have a 2004 tahoe lt with dual climate controls. My front a/c and heat work terrific. My rear a/c blows room temp and the heat works. When I first got the truck 2 years ago I didn't think the heat worked so I took off the blend door actuator I just recently got it replaced and it didn't fix my problem so I took it back off and used my hand to turn the blend door. Thays when I noticed the heat works great but the ac blows warm to room temp. I'm not an experpery nor do I know much about ac and heat on vehicles(just enough to get my by on the basics). Would anyone know where I can turn to next to look into?
 

LordWayback

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If it’s not the actuator/blend door and the switch is working you likely have a rear expansion valve problem edit: if you have to do the rear expansion valve you have to evacuate the refrigerant at a shop replace it and get it all back together this will be *Atleast* 5 hours of shop labor by my guess. 1 hour evac 3 hours Atleast working on expansion valve evap box more 1 hour recharging this is not a quick fix but as long as there’s not a evaporator issue/leaks it shouldn’t be insanely expensive. I would do your rear evaporator/heater core while you’re in there to prevent future leaks and well you already paid the labor and emptied your cargo area to access it. If you’re adventurous I would add a orifice tube into the rear ac lines because debris build up is generally what causes this issue in the expansion valve.
 
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LordWayback

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Expansion valves are buried in the evaporator box on the passenger side in the trunk 9/10 times when “front cold rear hot” it’s this $50 part that turns into a big deal.
 

LordWayback

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And actually if you need the expansion valve I have a spare I got lazy on my rig and didn’t install it but you’d still be out labor.
 

OR VietVet

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If you open it and it has debris in it, this needs to happen, accumulator replacement and orifice. If feeling money rich, do the heater core and evaporator too. This next step is important.....flush the system out and after doing that, you should have the lines all unhooked and replace all o-rings. It takes a special a/c flush and then blow out and let sit to dry about 1 hour, at least I always did when doing a/c work. Then evacuate the system and get as low on the vacuum inches as you can and leave on evacuator for at least 30 minutes if not an hour. Then shut off and watch the needle on the gauges and see if it holds the vacuum. If does not, you have a leak. If gets back up to 3" of vacuum but holds, no problem. Be a great time to replace schrader valves too.
 

rockola1971

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The rear AC system is plagued with GM factory problems. The rear HVAC control module has been updated. The warm/cool blend door falls apart at its pivots and gets stuck. There could be a bad blend door actuator. The wiring to the HVAC rear control module could be burnt at or near the plug. Then of course typical refrigerant related problems like bad txv, blocked txv or evaporator. Low refrigerant charge to the whole system.
Whats your pressure readings with bot the rear and front on max? Whats the ambient temp outside when you got the pressure readings?
 

bigdog96z

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rockola, my 2011 Yukon Denali just developed the problem with rear AC blowing hot all the time even while the front works correctly. you mentioned the blend door and possibly the control module plug. Where is that plug? We just recently had the airbags replaced for the recall and I'm wondering if the dealer tech unplugged it by accident.
 

OR VietVet

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rockola, my 2011 Yukon Denali just developed the problem with rear AC blowing hot all the time even while the front works correctly. you mentioned the blend door and possibly the control module plug. Where is that plug? We just recently had the airbags replaced for the recall and I'm wondering if the dealer tech unplugged it by accident.
@bigdog96z, you really should start your own thread in the correct section, about your problem. You can copy and paste the reference as well. You will get a better response to your problem that way. Plus, when you want a member's attention, put the (@) sign in front of their screen name and they will get an alert and get back to you. @rockola1971 will see this now and hopefully respond but hopefully a mod can move this post and alert you where it is, in the 2007 to 2014 section.

Also, I very much doubt that a tech did a recall for airbags on your vehicle and dug all the way in to the a/c control module plug and accidently unplugged it by accident. The techs follow a very specific set of steps to do any recalls.

By the way, almost 11 years in between the time you joined and your first post, is impressive.
 

bigdog96z

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Thanks for the help...we've had very good luck with the current set of GM vehicles...the 11 Denali and a 13 Avalanche so I haven't really needed the help of the forum although I do scan the weekly hot threads occasionally to see what is plaguing others. Now that I've said this I'll probably have a bunch of issues :)
 

OR VietVet

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Thanks for the help...we've had very good luck with the current set of GM vehicles...the 11 Denali and a 13 Avalanche so I haven't really needed the help of the forum although I do scan the weekly hot threads occasionally to see what is plaguing others. Now that I've said this I'll probably have a bunch of issues :)
You have awakened the beast
 

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