heater control

[eyehunter78]

I'm asking this for a friend. He owns a 2001 Chevy Subyuban and he can not control the temp it only blows hot air all the time if in off. Could this be the warm/cold switch that has gone bad or ?? Any help would be great as he would like to try and fix it himself. Thanks again.....

[K_Josh87]

Possible vacuum line issue? i do not know what chevys system is but Ford likes to use them, and IMO they are retarded... one comes off and the 4x4 won't work, and it defaults to defrost... Not sure what chevys have in them, but it'd be the first place i looked on a ford...

[Jeremy airjer W]

I'm asking this for a friend. He owns a 2001 Chevy Subyuban and he can not control the temp it only blows hot air all the time if in off.

Could you clarify this. The part that I don't understand is "it only blows hot air all the time if in off"? If what's in off?

There are no vacuum lines, it's all electronic.

Is this manual or automatic HVAC?

I would bet that the blend door actuator or the blend door itself but the HVAC module is a possibility. I'm thinking a scan tool would be the best bet to get some data on what the module is trying to do.

[eyehunter78]

Sorry, I meant hot air comes out vents even when fan switch is in the off position and the temp control is in the cold..It is a manual HVAC system. Also the rear air blows cold. Thanks

[Jeremy airjer W]

So the blower motor is running with the switch off or there is just air blowing through the vent as a result of you driving down the road?

[hanson]

Thats a blend door actuator (hot/cold).

Went through this on my 99 Sierra last summer and got everything fixed. First it was the blower motor resistor - fan only worked on high. Then it was my mode actuator (defrost/panel/floor/ect). And about the same time lost my control of hot/cold. So as I was driving around, I had heat coming from about everywhere, was definitely coming out the panel.

The blend door actuator is the one under the glovebox I think. Thats the easy one to replace. The other one is up above the gas pedal behind the dash, that one was a bugger.

[eyehunter78]

No fan blower running. Just warm air comes out of the vents

[Jeremy airjer W]

I would deffinetely check the blend door actuator.

[eyehunter78]

Thanks guys. It was the blend door it needed a new motor. Thanks for the help