Well this is a strange problem. I didnt even know it was possible to be honest. I turn the heat on in my Blazer and it doesnt seem to get hot just sort of a slightly warm but still cool air. This is with the heat all the way to 82 and the truck being driven for about 30 minutes. Any ideas?

 

coolant level ok?

 

Ooh good point, I havent checked yet. Ill be sure to do that first thing in the morning and let you know.

 

Heater core plugged? Blend door actuator bad or stuck?

 

Could be a vacuum leak in the blend ****. I had the same problem with my selector switch. Stick your head up to the actual **** and see if you hear a hissing. Mine had a bad seal. I also found that if I floored it, it drew enough vacuum temporarily and kicked it where I wanted until I replaced it.

 

Had both problems. Plugged heater core caused the exact problem described by the OP-little if any heat. After flushing the core and the rest of the coolant, back to normal hot heat.

Also had a bad HVAC vacuum switch - it would make a hissing sound and was slow to switch between defrost,vent,floor,etc. Surprisingly a new replacement switch was not available, so I got one from a junkyard.

Maybe I wasn't using the correct terminology? Isn't the blend door electrically operated by the HVAC temp switch?

 

Thanks guys, turns out the heater core was plugged. Had to have it back flushed but 84 bucks and I have heat again!