Only Hot Air coming out of my Vents

Hello All,

I have a 2004 Chevy Silverado (4x4 Extended Cab 5.3 L Engine) that only seems to “heat” the interior of the vehicle through the floor and dash vents. Hot air comes out of the vents no matter what I do ( I can direct this flow of hot air to the floor, dash, or both) . Even whe I use the A/C at the coldest selection it does not change the fact that HOT air is coming out of the vents. I am guessing that a door of some sort is “stuck” so that only engine heat is coming into the cab. Not sure if that is possible but just a thought. Anyone have any suggestions on whats going on? I am not sure if I should take it to the dealer or my local shop to have it serviced. Thanks in advance for any suggestions.

I am guessing that a door of some sort is “stuck” so that only engine heat is coming into the cab.

Probably, and you’re probably going to need the dealer.

Yes, this is a common problem with newer vehicles, as they HVAC has become more computer controlled with actuator motors controlling the doors rather than just a human activated cable. Sometimes you can see the problem by sticking your noggin up underside the dash while someone up top diddles the knobs. But often this proves to require the dash be disassembled to fix it and an expensive repair.

Both the blend door and the mode doors are operated with electrical actuators controlled thru the HVAC control module. The HVAC control module is what you see on the front of the dash with the HVAC controls. The odds that both door actuators failed at the same time would be rare. So I would focus on the HVAC contol module.


Ok. Sort of what I thought. Since I have a little time before the summer monthes I will check out what I can by looking under the dash/ moving the switches. Then I will call the dealer and set up an appointment.

I have a 2001 Chevy Blazer with the same problem, the actuators are vacuum operated, as vacuum hoses are connected to the actuators from a central block of hoses behind and under the climate controls. Thanks, at least I have a starting point, after I pull the dash again as I just replaced the heater core…


Your car’s HVAC system is VERY different from OP’s HVAC system.

With your system, vacuum plays a major role in the HVAC operation.

With OP’s car, vacuum plays no role, the actuator motors are controlled by the control panel, and they provide feedback.

So . . . even though you may have the same problem, you have totally different systems, and the solution may be quite different.

Sounds like the dealer is going to charge a bunch of money to tear it all apart and fix it. Wondering if I should ask my local garage if they can do this based on what you guys have diagnosed.

Your local garage should be able to determine if it’s the HVAC control module.


@sjd181 I believe your local NAPA store can get you Dorman brand preprogrammed HVAC control modules.

Plug and play and off you go . . .