Finally getting around to fixing my hvac issue, persistent for a over a year now that ive been ignoring.

None of my HVAC controls do anything. The lights change, but they dont change which vents the air comes out of, and no matter what i adjust the temp to, its roughly warm coming out of the defrost and floor that its been stuck on. I can change it to dash vents only and lower temp to cold but it wont actually change anything, though the lights on that button are illuminated.

I believe the AC button still cycles the AC pump on and off.

Some background on when this started - my center display radio/info center that travels up and down started to do the fuzzy on/off stuff, this was the first time i had ever noticed that(i bought this car used, so unsure if the screen flickered before i got it) and shortly after, my headlights began to not want to turn on, i would have to manually cycle the on/off until they came on, and then magically both fried at once(that wasnt cheap). And then the HVAC system quit responding. This all happened basically at the same time(all within days/a week), probably 2 years ago now. Was it all a coincidence or did that traveling wire deal short some stuff out? I never fixed the wire, the radio screen works 95% of the time so i never really cared enough to get into the dash. Is it maybe shorting and causing controls to be confused? I repaired the headlights(so fun removing the front fascia to change headlights), and ive ignored the AC long enough. Up near Tahoe CA i didnt need it much, but i just moved to Texas and its only spring and i can tell im going to need it bad.

I have a big fancy code reader, but when i had the dealer change the oil i mentioned it and they said "thats weird usually if the modules on the HVAC system fail itll usually throw a code" that dealership code readers can see, but he saw none. I could try mine maybe, but i have no dash anything indicating a fault.

Should i start with the "C7 HVAC Temperature Control Module" or the actual buttons control module first? Is it likely the HVAC box under dash has issues too that need fixing? My initial thought was maybe the electrical gremlin fried the motors on the air direction changers but that seems unlikely the more i research.

Any help would be greatly appreciated!

 

I have been having issues with my HVAC controls, too. Unlike your issue, my HVAC controls do not function at all.

The dealer replaced the HVAC module and the battery, but the climate controls still do not function.

When the dealer “fixes” the issue, the controls will function for 15 minutes and then turn off again. So, heat is coming out of the vents since that’s what it was last set to, but I cannot control it.

I am absolutely stumped.

 

does your radio do the flickering thing too? mine seemed to fail when that flickering started, at least as far as i can tell. i also believe that when the HVAC started to fail, i could cycle the buttons a few times to get it to switch finally to the desired vents, almost like the directional flap inside was sticking or something - it blew my headlights in a similar fashion - they started by not coming on automatically and having to cycle the on/off manually a few times before they lit up, but then blew them both at the same time. ide just like to find a solution and not have to go the 'throw parts at it' method as they arent cheap, and pulling the dash isnt easy. i believe the dealer quoted around 1k in man hours just to pull the dash, not including parts.

interesting in your case the hvac control module fixed it for 15 minutes - i wonder if the module blew that quickly? seems like something that regulates voltage is out - would make sense for my failures. did they ever replace the controls on yours, like the actual buttons cluster? have you ever had to fix your screens traveling wire?

 

Just some updates to this - today i replaced the control button electronic panel below the stereo display, and the HVAC control box above the glove box hoping it would solve my issues - it did not. I have the hvac blend door motors already, its just so much deeper into the dash - but other than them im not sure what else it could be. I checked all fuses and relays, swapped them around a lot(none were obviously blown). No changes. What other component is looped into the HVAC system? Not sure what to try next.

Interesting detail i forgot earlier - the same time all these issues started my next song button on my steering wheel only does previous song, so both song change buttons on the steering wheel do the same thing. Volume still works fine up/down.

This all started or started shortly after the first time the stereo display did the fuzzy short out screen. Cant think of what in the hvac system it could have fried. It seems so unlikely that it fried all 4 door motors at once, but its kind of the last thing to eliminate for me at the moment.

 

Like I always say dealerships only know how to replace parts…if they replaced the HVAC control module they should have checked the wiring…if you look below your steering wheel control switches and your HVAC module share a ground…G202 under the front of the passengers door sill…maybe check the ground…what year is your car ??…you should always put as much info in your profile because if I don’t see any info I look at your profile…wire diagrams vary sometimes every year…wiring is for a 2016…what code reader do you have…is it a scan tool ??

 

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