Heated seats flicker, and AC works only on the driver side

Hello folks,

I have owned my 2003 GMC Yukon Denali XL for many years and I have a couple of issues with it that have been ongoing since I bought it.

1) Heated seats have a mind of their own - been researching this one on this forum and wanted to run through it to see what would be recommended. Symptoms: Both front heated seats do not heat, heated seat lights flicker/blink and relay clicks (clicks under the driver seat I think) at the same time, sometimes multiple clicks and blinks in a second while I am driving with no interaction from me. If I press the heated seat button, the light lights up and will go out in a few seconds or less with no use of other controls. Power seats all work fine. Adjustable pedals go up and down, though the only appear to move from the lowest range of travel up maybe an inch or so. Looking under the dash, it appears that there is more range of travel up, but it does not go higher. Not sure if this is normal, but the buttons work and pedals move. Seat memory works and adjust seats to expected location changing between driver 1 and driver 2. I was considering replacing the brake pedal position sensor (tried searching for Google GM Technical Service Bulletin 05-08-143-001 but have not yet found it, but can continue searches). What would you recommend I change to fix the heated seats - brake pedal position sensor, DDM, driver seat bottom module?

2) HVAC issues - AC is functional on the driver side but the passenger side only gets heat. Digital climate control system (driver temp knob seems flaky with the temp number going lower when you try to turn it higher when its cold, but you can eventually get it to the temp you want with turning) Could this be a passenger side actuator? Also, air only blows out of the vents and not go to the feet or defrosters. Maybe a flapper blend door issue? I do not have the Tech 2 program but I should probably get it and need to figure out how to get the program and any associated cable...

Thank you!
Rob

Welcome to the forum from Virginia Rob. The intermittent electrical issues usually point to a bad ground or a weak battery. Start with the ground cables under the hood. They’re a known problem. You may find that it addresses the hvac issues too.

Thanks @Big Mama , the ground connections and strap in the engine bay look good and clean. I just disconnected the engine bay ground strap again and cleaned it well (see pic), no change in symptoms. Things like power windows, seats, mirrors, radio, locks, etc work consistently, the seats just blink and click and the issue seems isolated there.

The driver side temp knob can be a bit temperamental when cold., but once warm, sets the temp as expected. Probably the control head should be replaced from a similarly equipped denali. Maybe that would help the passenger side only heat issue, but that's just a guess - i probably need tech 2.

Thanks!
Rob

I believe that on the NBS the seat heater wiring under the seat can get damaged. Might want to check under the affected seat(s) for wiring and connector integrity.

I believe the ground for the control module is on the B pillar like mine. You’ll need to pop off the to see them. Also check your wiring while you have the front sill plate off. There are tons of wire there and it gets stepped on and kicked a lot.

Your heating element(s) in your seats may have gone bad as well. The click, flashing indicator and shut off are very indicative of that. Only way to check it that I have found (keep in mind I have not dove too deep into troubleshooting them in my own Yukon yet) is to replace the heating elements one at a time and try them out. (I would wager that someone has another way to test them with a meter possibly.)

Maytag87 said:

Hello folks,


1) Heated seats have a mind of their own - been researching this one on this forum and wanted to run through it to see what would be recommended.

Click to expand...

The window switch has the module that controls the heated function of the seats. Replace the switch and this will fix the flickering. Donot buy a used unit, it may also be defective. This is a known issue and GM put out a TSB on this issue. If the heated seats donot work is because someone disconnected the power to the heated elements. The flickering will cause the seats to get hot to the point that the vehicle is not drivable. The video below shows the connections you need to check. Start on minute 7:10.



[QUOTE="Maytag87,

2) HVAC issues - AC is functional on the driver side but the passenger side only gets heat. Digital climate control system (driver temp knob seems flaky with the temp number going lower when you try to turn it higher when its cold, but you can eventually get it to the temp you want with turning) [/QUOTE]


You need to replace the actuator that is on top of the dash, that is the hardest to do. I read on this forum that they can be cleaned up and they will start working again.

Replace the mode actuator and this will get the air blowing thru out the top and bottom vents. The video below shows you how to change out all the actuators. GL

Before you buy anything , get yourself a can of electric contact spray. Any auto parts store will carry it. I had similar issues with the crazy minded hearted seats. I removed the drivers door module and gave the contacts a good spray. I also sprayed the contacts under the seat. ALL that shit disappeared and the seats work perfectly. its worth a try for 5 bucks.