I tried to use my heater last night and found that all I get is cold air. The air comes out cold like the a/c is still on but the temp selector is turned to the right. It doesn't matter where I switch the vents to either, just cold air. Anyone know where I can start looking for the problem?

 

Two things come to my mind...

Bad thermostat (stuck open so you dont build up any heat)

or...I think that some trucks have had problems with the temperature control, the door that directs the air over the hot side or the cool side. It may be stuck on the cool.

Good luck.

 

The thermostat is a logical place to start. If your thermostat is stuck open then your engine will not get hot enough for your heater to function. You can check your thermostat by driving your truck for about 15 minutes to bring up to normal operating temp and put your hand on the upper radiator hose. If it hot (OUCH!!!), then your thermostat is fine. If it's cool or just warm then your thermostat is stuck open.

Do you have enough coolant? If your coolant is too low, your heater core will not have flow. The heater core or some of the hoses could be clogged as well. Have you been changing your coolant and using distilled water? These hoses are very small.

There is also a door that opens between Hot and Cold and if it gets stuck you will not be able to select between the 2. I read a story recently about a fella without A/C. He found that someone had put a pencil down the vent and it jammed the door on the A/C side so he could not switch. You would need to take your dash apart to confirm this.

 

Is that why sometimes when I switch from max cool to max hot I hear that door CLUNKING from time to time as it slams to the other side? It has never stuck yet, knock on wood! Just thought I'd ask...

 

My money is on a defective blend door. Might be a control problem or more likely a vacuum problem.

I'm assuming the original poster tried the heater with a hot engine. If not, then he'd definitely only get cold air depending on the position of his selector switch since the a/c compressor is on in most positions.

 

a month ago when i turned on my defrost, all that came out was cold air. couldn't figure out why, then figured out it was cause the **** turns but the control rod (for lack of a better term) that the **** goes on was not turning. I can verify this by a slight tug on the ****, which comes off and seeing the rod, which has one side straight and matching it up to the ****. None of that probably makes any sense reading it, but i sometimes have to push in on the **** and turn to get it to go where i want it. Haven't figured out why this is cuz the ****/rod are not stripped... anybody else had this?