'03 Blazer, over heating and no heat
 

My '03 Blazer is blowing no heat, only cold air. And is overheating bad. Checked my coolant level and it is fine. Any ideas???? I really need my heat back ASAP, it's cold in upper michigan.

Sounds like you have multiple issues with the cooling system that may not be related. Assuming your water pump is working the only other things it could be is the thermostat or mostly clogged radiator. As for the heat there are also two things...either the heater core is plugged or the blend door that makes the air go through the heater core is not working....both are common issues with the Blazer. After the truck is warmed up feel both hoses that go through the firewall to the heater. If one is hot and the other is cold then it's most likely a plugged core. If both are hot then it's most likely the blend door. I hope you have a garage to work in...it's pretty cold here too...only hit 62 so far.

Thermostat , water pump or improper antifreeze to H2O ratio. All the stuff dobyken said too but I would hope for just a jammed thermostat. Sounds like that to me. Don't worry about your heat, worry about your over heat. It will kill your car before you freeze to death inside.

Thanks for the advice. Sadly, no garage to work in. One of the perks of living in the U.P.

I just did a test run on it for a few minutes, and seemed to do okay till I got on the highway and went about a mile, then the temp started to climb fast, so turned it around and hi-talked it back home.
Checked the hoses like you said, they were both warm more towards the engine, then one was more cooler at the firewall.
So, I am guessing per your advice that it is leaning more towards the blind door???
And I will see if the weather is not to freezing this weekend and see if I can replace the thermostat, and getting a possible radiator flushed.

Do not drive the Blazer until you get the overheating problem fixed. Something else to check would be with the engine cold, take the radiator cap off, start the engine and let it warm-up and watch the coolant level in the radiator. It should be flowing...if not, then the radiator is clogged-up and hopefully a flush will clear it.

Do not let the engine overheat.