2017 Suburban LT with 100k miles. AC started occasionally not cooling from dash on both drive and passenger sides. Rear air works as it should. Both rad fans are turning. Freon levels are good. Driving down the road (nearly all the time - I think), I get 58 from the vents on a 90 day. Sitting in the car at idle, I'm getting 80 from the dash vents and 58 from the rear ac. I can get cold air (same 58 as rear) from the dash if I hold the idle at 1k or so and have the blower on medium. If I let off the gas and let it go back to idle, dash vent temps start to rise to 80 while rear continues blowing cold.

Considering I get cold air off and on -- and this happens during same ride, I'm currently at a loss. A hunch blames an actuator inside the dash or a sensor causing it to act weird, but I really don't know.

Any ideas?

Thanks

 

We've had under-dash actuator issues on

...our 1994 Suburban
...our 2005 Yukon
...our 2014 Yukon

...1994 Suburban - paid mechanic about $400 to fix
...2005 Yukon - bought aftermarket actuator and ground a 5.5mm socket shorter and replaced myself
...2014 Yukon - removed actuator, cleaned out old grease, put back together to fix

I believe it was the same actuator that failed on each. These actuators open and close the flaps the allow or prevent air from moving through the dash vents.

 

Since the cooling gets better when the engine RPMs go up, it might be an airflow or fan speed issue, not just the refrigerant levels. Check the blower motor and its resistor because they control the fan speed. They could be malfunctioning or partially blocked, especially at lower RPMs or when idling.

 

Any update? I have exactly the same problem recently on my 2017 Tahoe