Auto climate control issue

[jasonLmarsh]

Just picked up a nice 2005 Z71 Suburban and having a strange issue with the HVAC. The issue is that the AC blows ICE COLD from all the vents all the way up to about 90, where it switches to full hot. The fan speed starts decreasing around 80 degrees on the hvac, but it's still blowing ice cold air. At around 90 it will switch to full hot. I'm thinking this might be one of the blend door actuators, but not sure which one since all the vents across the dash are in sync with each other. I did replace the fan/sensor module in the headliner with a GM part since the old was was buzzing. Is there another sensor I should change? or could this be a blend door actuator?

 

[stutaeng]

Those are the exact same symptom my 06 Suburban had, but I replaced the headliner temperature sensor and it got fixed...

The blower slows down when you set it to 80? Umm, that's not supposed to happen...

I think a scanner with bi-directional controls should be able to override the blend door actuators(?) That way you can rule that out. Or crawl under there and try looking with an inspection mirror to see if you can spot the shaft/gears moving as you move the temperature. It's the one on the passenger side I believe.

Welcome to the forum BTW.

 

[jasonLmarsh]

Thanks for the warm welcome and the comments. Yes the fan slowly starts decreasing as you increase the temps from around 75-85. It's still ice cold, just blowing slower. I think once it hits around 90, it flips to heat mode, then the under-dash vents blow full hot. After I replaced that sensor, should I have done the hvac reset? I may give that a shot too, then I'll look to see if I can verify if the actuators are turning.

 

[Tonimus]

Welcome to the forum! There's no reset needed according to OEM info, but there ARE two sensors according to the book.

Inside Air Temperature Sensor, Replace
Auxiliary

1. Remove lefthand rear door sill trim plate.
2. Remove lower rear seat belt cover and bolt.
3. Remove lefthand third pillar trim panel and rear coat hook.
4. Remove rear headliner retainers from front headliner.
5. Lower headliner from roof retainers.
6. Disconnect inside air temperature sensor electrical connector.
7. Partially remove inside air temperature sensor from headliner, then remove sensor grille from inside air temperature sensor.
8. Remove inside air temperature sensor from headliner.
9. Reverse procedure to install.

Front

1. Remove left windshield garnish molding.
2. Remove left center pillar assist handle, then the left center pillar garnish molding.
3. Remove left sunshade.
4. Pull down on headliner.
5. Disconnect inside air temperature sensor electrical connector.
6. Partially remove inside air temperature sensor from headliner, then remove sensor grille from inside air temperature sensor.
7. Remove inside air temperature sensor from headliner.
8. Reverse procedure to install.

 

[jasonLmarsh]

Thanks for that. Since this all seems to be related to the front zone, do you see any need in messing with the rear sensors?

 

[Tonimus]

No idea. But anything is possible.

 

[ORVietVet]

Welcome to the forum, from Oregon.

Easy directions for a reset on you tube. I would at least try it.