So I have no heat, the blower still blows at every setting. Did a heater core flush with a little bit of gunk coming out, but not as bad as I would've expected running orange dex-cool. Drove the truck around for a while and discovered it blows slightly warm air out of the defrost and floor settings, but ice cold out of the dash vents. Popped the hood when it was still hot and checked the coolant level, it was right where it should be. Checked both hoses going into the heater core and each was very warm. Not hot where I couldn't hold it but both equally warm. The temperature gauge on the dash reads where it has always been, at about 190 or so.
This one has got me kind of confused and I couldn't find any other posts like it. Also I first noticed no heat the same day I put a new battery in my truck. I doubt its related but who knows?? I gotta get this fixed, winter in Minnesota is almost here in full force...thanks in advanced for anyone that helps me out.

 

is the blower shot?
maybe the heater core has just taken a dump all together aswell?

 

I don't think the blower is bad. I replaced that last winter. If it was bad wouldn't it just not blow at all, on any setting? Also I don't know if the heater core is shot or not, but I don't have any noticeable coolant leaks, and no smoke or smell coming out of the vents when I turn the heat on. I've been reading about a "blend door actuator" or something like that around here, any possibility that could be it?

 

I recommend refilling your antifreeze with your Blazer's front end up on ramps. This really helps get the air out and keeps you from having air bubble floating around.

If you look on your Blazer's firewall, you'll see the HC inlet/outlet lines are really up high compared to the engine.

I hope that helps you out!

 

did u burp it after the flush??

run the truck from cold to warm up with the rad cap off, when the thermostat opens it will bubble and sputter use a rag and close the rad cap. (helps to get remaining air pockets out) also when idleing from COLD!!!! slowly squeeze and release the upper rad house to help push the coolant thru the system

works on hondas, should work on a gmc

 

yea possibly theres air in the system

also when you flushed it did you make the water go the opposite way then it normally runs ?

 

I did not burp it after the heater core flush. There may be air in the system, but I had no heat before I did a flush either. I just went out and started my truck again while it was still warm and something interesting happens. This might be hard to explain but, When I have it on defrost it blows hot for about the first 20 seconds the vehicle is running. After that it makes the fan noise as if I switched the temperature dial to the middle, and blows out lukewarm air So my (novice mechanics) thoughts so far are....I don't believe it is the heater core, as there was no smell or coolant leak. Also the lines in and out are warm, and not much gunk came out when I flushed. There could be air in the system, but I'm starting to think its some kind of switch or relay????
ALSO I totally forgot to include some info....I have a 98 Blazer LT with the automatic temperature control.

 

my 93 was the same way,couldnt get anything but slightle warm air! I drove it 7 northwest Pa. winters like that before i found the fresh air vent open. Its behind the rt side kick panel , try lookin there!!!! Hope it helps!

 

I think you've got air in your system bud. Try burping it and let us know what you find.

 

I found out the problem actually was (still is) with the blend door! When I would start it with the heat and blower on full blast, it would blow hot air like it normally would, but then for some reason the blend door would switch itself to cold air. To temporarily solve this for the winter, I popped down the glove box and started the truck, and then before it had a chance to switch itself to cold air, I just disconnected the electrical connector. So at this point the blend door is stuck on hot, which is better than stuck on cold air at this time of year. I will likely replace it this spring when I get some time and money but for now its temporarily fixed. Thanks again for all the help everyone, great forum here.