Front A/C not Blowing Cold

[jwrussell]

2015 Yukon XL Denali, ~75k mi

Anyone have an idea why my front vents (main, floor and defrost) will only blow ambient air temp or warmer? The rear vents will all blow cold.

I've played with every setting I could think of to make the front blow cold, and it just won't do it....
My normal setting is 70 on Auto.

I could only find one other similar post, and it didn't have a solution:
https://www.tahoeyukonforum.com/thr...ck-ac-is-ice-cold-front-will-not-cool.113309/

Any help would be much appreciated!
Thanks,
Joe

 

[swathdiver]

2015 Yukon XL Denali, ~75k mi

Anyone have an idea why my front vents (main, floor and defrost) will only blow ambient air temp or warmer? The rear vents will all blow cold.

I've played with every setting I could think of to make the front blow cold, and it just won't do it....
My normal setting is 70 on Auto.

I could only find one other similar post, and it didn't have a solution:
https://www.tahoeyukonforum.com/thr...ck-ac-is-ice-cold-front-will-not-cool.113309/

Any help would be much appreciated!
Thanks,
Joe

Joe, one or more of your actuators is stuck/broken. You need a bi-directional scan tool like the MDI2 with GDS2 software to see what the truck's computers are seeing. There are probably internal codes stored in the BCM about this.

 

[jwrussell]

Joe, one or more of your actuators is stuck/broken. You need a bi-directional scan tool like the MDI2 with GDS2 software to see what the truck's computers are seeing. There are probably internal codes stored in the BCM about this.

Yeah, that's kinda what I had come to the conclusion of, too. Unfortunately I don't have that kind of hardware to troubleshoot, so it's sitting at the local shop today. Hopefully he can point me to the problem....

In the meantime, anyone have any idea which actuator this sounds like? My research shows there are a handful, and I'm run-ing out of time to troubleshoot before leaving on vacation (road trip) Saturday.

All the help is much appreciated!

Joe

 

[OR VietVet]

Could also be the controller panel itself but the actuators are known problems, as @swathdiver said.

Also, welcome to the forum from Oregon. Another also:


We recommend that you put all your rig(s) info in your signature so we all don’t have to guess at year, make, model, engine size, trans, rear axle locker…….etc. While you may have posted pertinent info in your first post, you may forget to do it again and the info is needed by us anyway. Makes it way easier on all members that attempt to help, to have that info right up front. It is also recommended that you take a pic of your RPO codes, on the inside cover of the glove box, and post that image in your signature. All this info will greatly help those that will try to help with a problem.


If there is any other info, like upgrades, mods or recent mechanical/maintenance work done, that would be helpful in any post as well. Too many times a question is asked by the poster and after about 10 responses we find out that the poster has done recent work to attempt to fix the problem or work that was done that SEEMS not related to the problem.

 

[swathdiver]

Yeah, that's kinda what I had come to the conclusion of, too. Unfortunately I don't have that kind of hardware to troubleshoot, so it's sitting at the local shop today. Hopefully he can point me to the problem....

In the meantime, anyone have any idea which actuator this sounds like? My research shows there are a handful, and I'm run-ing out of time to troubleshoot before leaving on vacation (road trip) Saturday.

All the help is much appreciated!

Joe

There are 4 actuators up front and two in rear. The mode actuator controls which vents the air comes out of, the recirc actuator controls the amount of fresh air allowed into the system and the other two control the temperature for the driver and passenger. As Ron said, it could also be your controller, the panel under the radio. If the shop has a bi-directional scan tool, they'll know in seconds what is wrong.

Consider getting a VXDIAG Nano with GDS software for yourself in the future, it will quickly pay for itself.

 

[OR VietVet]

RA shows three options for the controller, I just picked one.

https://www.rockauto.com/en/moreinfo.php?pk=6849528&cc=3307644&jsn=2206

 

[jwrussell]

There are 4 actuators up front and two in rear. The mode actuator controls which vents the air comes out of, the recirc actuator controls the amount of fresh air allowed into the system and the other two control the temperature for the driver and passenger. As Ron said, it could also be your controller, the panel under the radio. If the shop has a bi-directional scan tool, they'll know in seconds what is wrong.

Consider getting a VXDIAG Nano with GDS software for yourself in the future, it will quickly pay for itself.

Thanks Swathdiver. From my 'playing around with it' it seems like those 4 actuators in the front are working properly. I can switch between vents, re-circ seems to be working normally, and I can control each side independently (just only to make it hotter...).

I assume the two actuators in the back are a mode (change between ceiling and floor) and a temp control? Can't see how either of those would affect the front, though...

The fact that I'm continuing to get cold air in the back makes me hesitant to believe there's a leak anywhere. Additionally, a leftover cheapo gauge from a parts store refill bottle reads dead center of the green band (~35-40psi).

What about an expansion valve? I'd love to have a full system diagram, but I don't.... are there two expansion valves and evaporators in this system (front and back)? I'm not sure how an expansion valve stops working, but if the front one did, I'd have no cold up front, but the back system would be unaffected, right?

I'm just thinking out loud here.... I appreciate all the feedback.

....and yes, I would love to have a diagnostic scan tool. Any recommendations for a MAC (non-windows) user?

 

[swathdiver]

Thanks Swathdiver. From my 'playing around with it' it seems like those 4 actuators in the front are working properly. I can switch between vents, re-circ seems to be working normally, and I can control each side independently (just only to make it hotter...).

I assume the two actuators in the back are a mode (change between ceiling and floor) and a temp control? Can't see how either of those would affect the front, though...

The fact that I'm continuing to get cold air in the back makes me hesitant to believe there's a leak anywhere. Additionally, a leftover cheapo gauge from a parts store refill bottle reads dead center of the green band (~35-40psi).

What about an expansion valve? I'd love to have a full system diagram, but I don't.... are there two expansion valves and evaporators in this system (front and back)? I'm not sure how an expansion valve stops working, but if the front one did, I'd have no cold up front, but the back system would be unaffected, right?

I'm just thinking out loud here.... I appreciate all the feedback.

....and yes, I would love to have a diagnostic scan tool. Any recommendations for a MAC (non-windows) user?

An actuator can be out of spec and still work, and they can get stuck and unstick themselves. So don't rule them out until you can see the codes. GM uses the MDI2 interface with GDS2 software. You can get a clone of this tool off of Ebay and other places but I do not know if the software works with MAC. You might buy a little $100 tablet and connect it to that. VXDIAG NANO is another option with GDS software, just make sure it includes your truck. I am not up to date on the software required for yours.

As for valves and pressures, don't really know enough. I bought a manifold and made a cheat sheet as to what the pressures mean on the Hi and Low sides. My father over-filed his Kia the other day and the gauge said green but the AC shop said he put too much in it. They did a complete evacuation and then refilled it which is the proper procedure.