No hot air with new heater core

[tahi]

I recently changed my heater core on a 98 blazer with electronic climate control. I had a hard time removing the dash but I could finally replace the heater core with a new one, and I've no leak. The trouble is that from now I don't have hot air coming out of the vent outlets! I checked (with the dash on) all the vacuum lines and everything seems to work OK about switching form feet to windshield and so on. On the engine side both heater tubes that come from the engine are hot.
My question is : does someone know how the hot/cold air works close to the heater core. Is this a door vacuum activated or something else. Would be great if I could go snowboarding again this winter

[tahi]

In fact, my question is : is the temperature door the only part that controls the hot/cold air that run into the vent system?

[ls1s10onair]

u answered ur own question... electronic climate... the head unit is probably bad... the blend door is electronic, controlled by the head

[orangesonoma]

stupid question.. did you fill up the coolant after you did the swap? like did you top it off?

[tahi]

Quote: Originally Posted by orangesonoma

stupid question.. did you fill up the coolant after you did the swap? like did you top it off?

Thanks cuz I could have forgotten after the dashboard removal hassle but I did a complete refill.

For what I saw on my truck the temp door is relies on a little electrical motor. I checked and this motor is actually rotating but I don't know what's the angle range of the temp door? 10° 30°? If someone knows that, it would be helpfull.

[Goran]

did you change your thermostat?

[bonjourblink182]

There is likely an air pocket in the system that is keeping coolant from entering the heater core...I have done coolant changes on two other blazers, one my own and one a friends and I ended up with air pockets in both for some stupid reason...

to get it out, I think you run the truck with the Radiator cap off and it will find its way out sometimes you rev it a little to up the pump pressure of the water pump....MAKE SURE YOU TOP OFF THE ANTIFREEZE or you run the risk of overheating your truck.

someone second that...I'm pretty sure thats how thats fixed but not entirely.

[Kicker]

i would say put more coolant in ur overflow tank. i lost some coolant due to a leak where my coolant sensor is, mine wasn't pushing warm air till i added some fluid

[brokes10guy]

Quote: Originally Posted by bonjourblink182

There is likely an air pocket in the system that is keeping coolant from entering the heater core...I have done coolant changes on two other blazers, one my own and one a friends and I ended up with air pockets in both for some stupid reason...

to get it out, I think you run the truck with the Radiator cap off and it will find its way out sometimes you rev it a little to up the pump pressure of the water pump....MAKE SURE YOU TOP OFF THE ANTIFREEZE or you run the risk of overheating your truck.

someone second that...I'm pretty sure thats how thats fixed but not entirely.

I had The Same problem on my blazer when i did a coolant flush all i did was took the radiator cap off and let it run reving it up every now and again. i left the heat off for about 10 mins or so the cranked it on high untill i had heat. i just checked my haynes manual and it says to fill up the radiator and let it runtill upper radiator hose it hot and then top it back off and put the cap back on.

[bonjourblink182]

sweet i'm not crazy then...lol

[94S10asm]

i have the same problem yesterday i replace my thermostate in my s10 and now i got no hot air and the water temp doesnt stay constant so i just need to take the cap off and run it for a while and air will work its way out?

[bonjourblink182]

yup then refill the radiator...thats the important step