I have read through all of the heater posts and I still have questions. First off, I have a '98 blazer with the computer controlled climate and the heat doesn't blow warm air. I have checked the hoses going to the heater core and both are hot and I have verified the coolant levels in the overflow and radiator. I have also just recently changed the t-stat and the engine warms up to the correct temp. I've read about a door that should be opening (or closing) when I turn the temperature **** to heat. Can someone let me know where it is located and how to verify the operation of it? The air comes from the proper places that I select, ie; defroster, vent, floor and the AC works fine. The termperture doesn't change at all when I go from cold to heat and I can't see anything moving behind the glove box.

Please help, I'm tired of being cold....

Thanks.

 

I'm asking a friend of mine about this... he is a shop forman at a chevy dealer. i hope to have some suggestions for you soon... since no one has answered you yet.

 

Ok heres what I got:

usually the heater core clogs. if its not that, then the blend door actuator isnt switching its under the dash, ask if he hears the motor running as he switches from hot to cold if not, it may be a blend door... but the cores are known for getting mucked up try flushing out the cooling system with some vinigar or even baking soda

 

I don't think the heater core is clogged since both lines going to it are hot, but I guess I can try to flush it anyway. It was also replaced a couple of years ago. Any other ideas?

 

flushing the heater core worked PERFECT for me...I had the same symptoms and that cleared it right up! try it

 

The vent door actuator is behind the glovebox, just push up on the metal stop at the back and all the contents of the glovebox will fall onto the floorboard...that will drop the glovebox and you should be able to see behind it. There will be a big black plastic box with the actuator on top...rotate the temp **** and watch it to see if it moves...if not then either the motor or the connector/wire are damaged (not working)....

 

I don't see anything moving when ever I move the temperature dial. I do see something move when I go from the floor vent to the dash vents. It has the gray vacuum hose going to it. That is the only thing I can see on the top of the black box. I will try to look again, also there is nothing in the chilton's book about any of this....

 

I just flushed out the core and it did have some junk in it. Now it seems to be doing something different. It doesn't matter if I set the dial to cold or hot, it blows hot air for about 5 to 10 seconds and then it blows cool air for 5 to 10 seconds. I can now hear something switching behind the glove box. When ever I lowered the glove, I can't see anything moving back there, but I can hear it. I guess it's the blending door opening and shutting, but I'm not sure. It seems that when it blows cooler air, the volume of air is greater than when it's hot. It also is extremely hot now. The thing is that it's hot even when I have the fan off or if I have the AC on or off, I can still hear it the door switching open and closed. It doesn't change no matter what I have the dial set to. I can have it set to blow from the floor vents or the dash vents, and the defrost vents and it still does the same thing.