Heater issue

[BowtieMafia66701]

So my heater decided the other day to start acting up. I am not getting good air flow from my front vents for heat. Now it is hot but i get very little out of the vents except the defrost vents on the dash works great. Ive tried every setting but still very little air flow out of the floor and dash vents. I ve seen where i should check my cabin filter and or a blend door actuator and also where i could try a hvac and ac reset by popping those fuses. But I do need to replace my rear blend door actuator because the rear just blows cold. Just looking for what i should try first. It only started doing this a few days ago. Any help on where i should start would be appreciated. Thanks

 

[Joseph Garcia]

truck year, model, trim would be helpful information

@swathdiver

 

[BowtieMafia66701]

2003 tahoe LT

 

[swathdiver]

There are 4 actuators up front and 2 for the rear AC. You really need a bi-directional scan tool that can read BCM codes and interact with the actuators to test them out.

Without the Tech-2 type tool, we're guessing. My guess would be the Recirc actuator is either not closing all the way, bleeding off volume and cool air or the foam material on the door has started crumbling leaving a gap causing the same conditions. If the rear is always cold but does cycle through the modes, that would be the auxiliary temperature actuator.

The actuators are like servos on radio controlled airplanes and such. Inside the box are plastic gears and these usually crack causing them not to work right anymore. Some folks glue them back together and the repair is a success. I didn't want the down time when doing mine, just replaced them with new GM ones.

 

[BowtieMafia66701]

Well the rear blows cold. But the front is still hot. So i figured for the rear i might need to replace the rear blend door actuator. Havent really cycled the rear i just got the tahoe a few weeks ago but noticed the rear was blowing cold while the front wss hot but when i tried it then it flowed good now i tried it in the am when it was semi cold it started this.. But yeah all i have is a basic obd scan tool. Sounds like i might just have to take it to a guy i know who works on cars air systems. I dont wanna replace the rear blend door actuator if its something else.

 

[BowtieMafia66701]

Went out and played with the rear controls it all engages and i can hear it change when i change settings. Now upfront it just stays the same weather i have it on defrost, floor or vents and the circulation i hear nothing and it dosent engage or do anything at all.

 

[BowtieMafia66701]

Ok so after find its location which is by the gas pedal i assume this is the ricirc accuator. I was told to unplug it and on the side of it should be a gear type lever and if its on defrost it would be stuck at the top so i rotated it down and now i have heat coming out of the vents really well now. Just not out of the defrost vents. So this is the one that needs to be replaced i am assuming.

 

[Fless]

You may also need to have a "calibration" updated on your HVAC control unit (which would be a programming update done by a competent shop or the dealer). I don't know if you have the manual HVAC or the AUTO HVAC, but it might be worth checking into. IIRC @SnowDrifter had it done recently.

 

[BowtieMafia66701]

I have the auto.

 

[Fless]

It sounds like you're setting the temp and fan speed, using the controls manually, right?

But if in AUTO, where the HVAC control manages the fan speed, it uses sensors in some of the ducts to sense the air temp. Those won't cause your issue if you're operating it manually.