2003 Malibu heat on full?!?

[snappy|nuts]

I have a 2003 V6 Malibu and for some reason the other day the heat just decides to stick on full. When I turn the temp dial to cold, and even put on the A/C, nothing but scorching hot air comes out of the vents. I can turn the blower off but when driving, but hot air is still forced through the venting system.

any ideas? I checked fuses and nothing seems to be blown. I am at a loss..... the next step I was going to go for was replace the dash dial assembly.

thanks

[dpalomaki]

Does the car have a manual or automatic temperature selector for the HVAC controls?

The fan/coil unit contains two heat exchanger coils, one for cooling (evaporator coil) and one for heat (that has coolant circulating through it at all times). The outlet air temperature is adjusted by a mixing door that regulates the amount of air from each coil. Sounds like the door is stuck to allow mostly or only air from the heat coil.

In an automatic air temp car this could be caused by a bad door actuator/controller. On a manual air temp car it could be a failed or disconencted control cable somewhere at or between the door and the temp selector.

[snappy|nuts]

I have the manual temp control.... sometimes when I start the car up it does stick on cold too.... it's either full out cold or full out heat!.... I'm assuming the door that controls hot/cold air is not easy to get at to check?

Thanks for the response by the way!

[dpalomaki]

I've not worked on that part of a Malibu HVAC system, so I do not know for sure, but I suspect it is a bit awkward to reach but not especially difficult if yo are comfortable working in/behind the dashboard. The feel of the temp control may give you some idea what is happening. If it move very freely the control cable may be disconnected or broken.

The details should be found in any decent service manual for the car.