No heat, all of the vents in the front blow cold when the thermostat is in the hot position?

KPIRTHIPAL

MEMBER
2007 CHEVROLET TAHOE
5.3L
V8
4WD
AUTOMATIC
110,000 MILES

My aux heat works fine but all of the vents in the front blow cold when the thermostat is in the hot position. I don't think it's the blend door actuator because I am able to change between blowing air to your feet and blowing to your face without a problem. I'm not sure what I need to replace. I don't think it's the heater core since I get heat out of the aux (rear vents) without a problem.

Friday, January 27th, 2023 AT 5:12 PM

1 Reply

JACOBANDNICKOLAS

MECHANIC
110,176 POSTS

Hi,

The direction of the airflow is controlled by a mode door actuator. The air temperature entering the vehicle is controlled by a blend air door. (They don't make it simple) LOL

On this vehicle, there should be two blend door actuators (air temperature actuators). One for the left and one for the right. Are both sides equal in temperature?

If they are, I want you to try something for me. Start the vehicle and turn the heat on high in the front. Allow the engine to reach operating temp. Once it does, turn the engine off and open the hood. Feel both heater core hoses near the firewall where they attach to the core. See if both are hot. If they are, we have an issue with the air temperature doors. If one is hot and the other isn't, then the heater core is likely clogged.

Also, take a look at this link. You may find it helpful.

https://www.2carpros.com/articles/car-heater-not-working

Let me know what you find.

Joe

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Saturday, January 28th, 2023 AT 10:04 PM