Blower motor works great, air coming out of all the vents as it should just the wrong temp. I had the vacum motors under the dash replaced last year when I had air coming out of the wrong places now the temp will not adjust any ideas????

I did back flush the heater core last week just to make sure it has good flow.

 

I am having the same problem with my truck all the controls work, but the thermostate does not change anything. It just stays cold, like their is an a/c butten that is stuck on or something.I have been told that the heater coil could be stopped up because of the using of dex-cool antifreeze. And thats not hard to believe just take a look down in your radiator if there is large rust deposits in it. This could be the case but only time will tell. I will let you know what my finding are but not today I have already got a hugh honey do list lol.

 

The heater core is easy to check/back flush if you think it is clogged up. Just remove the two hoses comeing out of the firewall that run to the motor and, use you garden hose to push water threw them one at a time. I used a 5 gallon buck to catch the water coming out and it made almost no mess.

 

This Blazer has been nothing but problems since the first day I drove it. If I cant get it fixed soon I am going to rid myself of this headach.

 

Well I woke up this morning and had a to do list for the truck. Anyway I started by putting the oil cooler lines mounting bracket back on, just one bolt that I didnt put back on when I installed the motor. Then I made me a flushing hose out of a old washer machine hose I had laying around at the house, and flushed out the heater coil both ways it was black as you could admajin and the best part is that it fixed my no heat problem. And I thought of you and rushed in hear to let you know just flush it out and youll have heat. All this started because it was the first day this year it got under 50 degrees.

 

okay i had heat some what now i dont really have any because its getting coder here in mass, im having an issue determining why i dont have heatmy upper radiator hose is hot but the lower one stays cold? i do have an issue with my blend doors it doesnt matter what i set the vents on it always comes out the defroster but when i put it on defrost you can here it kick over to defrost? im about to put in a new thermostat becausei do belive thats the reason its stuck open i could be wrong , i do know that its common in the blazer to crack the heads if your not watching your coolant level and loose coolant thru the intake gaskets or head gaskets so what ive done is put on a 7 lbs radiator cap to save th heads or intake was that the right move? any advice is highly needed thank you

 

Flush your heater core first. Changing the thermostat is probably ok too. Blend doors are most likely a vacuum issue. Solutions have been covered thoroughly here.

 

thanks aa21830,
but i have seem to have found the problem a very small pin hole leak in my radiator