I put this in the general topics section yesterday witout much feedback yet. A guy at work has a 01 Silverado 4.8...says sometimes the heat can't be shut-off...any help on this?

 

1) Technically the air is always on in the vehicle. If you have the dial all the way to the heat position it is going to throw out hot air no matter what. Even if you have the fans(blower) turned off. If you have it all the way to the cold postion it is going to throw out cold air not matter what (not AC cold but air that is as cold as the outside air). What I just do is set the dial in between.

2) Now if it is throwing out hot air even when you turn the dial to the cold position, the cable that opens and closes the the cold/heat vent might have broken off, or fell off. Now before on every single car that I have ever messed with there is always this cable or rod that opens and closes this vent. I am not sure if our trucks have this cable or rod... it might be sometype of vaccumm or it even might be run by something electrical even. I really do not know. But in any case this is usually the problem when you can't switch from warm to cold or cold to warm. maybe someone could chime on on this.

3) What I would do is take the panel out, carefully pull out the radio (there are some slide in clips on the radio) and see what type of device makes that vent open and close it. If it is a cable.. follow that cable and see if it is opening that vent.... Sorry if I was not that much help.

 

Thanks for the reply. He said it has done it only a couple of times so far. I just asked him about it again and it pushes warm air even with the ac on.
I called a guy on a radio talk show a couple days ago and he said possible low water level,control motor or a programmer.