More HVAC fun. Anyone seen this?

[Pressureangle]

Sooo... '04 Yukon XL 2500 SLT. Auto climate control, split front with rear on upper console.
It's had intermittent fixes through it's life, and until recently was good; this issue began this past summer when I acquired it from family after it had sat without driving for a couple years. Sunroof leaks left an inch of water in the driver's floorboard. Symptoms initially were it stayed hot on the driver side, but if you keyed up the ignition and let it cycle the dash lights before starting it would work properly. Eventually it got worse until now, the punch line; When it got cold, the driver side stayed cold. When it got warm, the damn thing went hot and in neither circumstance could you change it. WTF? Maybe the temp sensor has gone nuts... I have the split door controller in hand but yet to install. Wondering if a bad actuator can confuse it so bad, but the actuator moves... but not as it should. Of course, the interior was wet and humidified so all the connections will be suspect, DeOxit-ified and remade along the way but wondering if I should find and replace the temp sensor(s) as well while I have the dash apart.

Anyone?

 

[Doubeleive]

Sooo... '04 Yukon XL 2500 SLT. Auto climate control, split front with rear on upper console.
It's had intermittent fixes through it's life, and until recently was good; this issue began this past summer when I acquired it from family after it had sat without driving for a couple years. Sunroof leaks left an inch of water in the driver's floorboard. Symptoms initially were it stayed hot on the driver side, but if you keyed up the ignition and let it cycle the dash lights before starting it would work properly. Eventually it got worse until now, the punch line; When it got cold, the driver side stayed cold. When it got warm, the damn thing went hot and in neither circumstance could you change it. WTF? Maybe the temp sensor has gone nuts... I have the split door controller in hand but yet to install. Wondering if a bad actuator can confuse it so bad, but the actuator moves... but not as it should. Of course, the interior was wet and humidified so all the connections will be suspect, DeOxit-ified and remade along the way but wondering if I should find and replace the temp sensor(s) as well while I have the dash apart.

Anyone?

the best thing to do is use a tech2 to really figure it out, I would be less concerned about any sensors in the ducting and perhaps consider the one in the headliner instead as it is the one that makes the adjustments when on auto. the actuator could be funky as well they are pretty basic just a motor a copper contact and the gear.
without looking at the tech2 data though it's pretty much a guess unless you can see a defect.

 

[Pressureangle]

the best thing to do is use a tech2 to really figure it out, I would be less concerned about any sensors in the ducting and perhaps consider the one in the headliner instead as it is the one that makes the adjustments when on auto. the actuator could be funky as well they are pretty basic just a motor a copper contact and the gear.
without looking at the tech2 data though it's pretty much a guess unless you can see a defect.

ah yes, I just acquired an OTC Genisys Evo scanner, but it's my first non OEM/PC based system ... I guess I'm going back to school for a bit. Is there a good resource for the actual locations of the components- all the actuators and their zones, temp sensors, etc?
FWIW the rear system works as it should.

 

[adventurenali92]

I’d put money on the automatic ambient sensor mounted in the headliner just above the drivers seat being screwy. You mentioned a sunroof leak and that sensor is just rear wards of the sunroof definitely in the path of a potential sunroof look. It probably got wet.

 

[S33k3r]

His symptoms also describe what I experienced when we lost the driver's side blend door on my 2004 Silverado 2500. But I believe that is one of the two that can be replaced WITHOUT pulling the dash.

 

[Doubeleive]

ah yes, I just acquired an OTC Genisys Evo scanner, but it's my first non OEM/PC based system ... I guess I'm going back to school for a bit. Is there a good resource for the actual locations of the components- all the actuators and their zones, temp sensors, etc?
FWIW the rear system works as it should.

drivers side actuator is under the hvac box/under glove box, passenger side is on top of the hvac box behind the srs airbag
up/down actuator is way under the center of the dash hard to get to but not impossible