The heat stopped working in my 2000 Blazer. Fan blows from vents and floor but no heat and the temp. gauge is barely rising after the engine is warm. How can I fix my heat?

 

possibly you have a failed " fail-safe" thermostat or your gauge is incorrect , usually you will also run rich with a stuck open thermostat such a failsafe unit , grab the heater core hoses at the firewall , both should be about equally as warm , if not you have a classic clogged heater core . backflush if 1 is colder than the other ( usally the outlet or right hose at firewall )

 

Most likely your thermostat is stuck open. I've had my heater core back-flushed numerous times, I finally told them to put the old green antifreeze in it. Never clogged again.

 

I too am a believer in the green. One product on the shelf and never had a problem with it.

 

Check your heater blower motor resistor.

 

Blower motor resistors are fine as the original poster stated that the fan blows air, just not warm.
Very likely stuck thermostat. Easy to change, a bit messy though. I suggest draining the radiator BEFORE taking the upper radiator hose off the thermostat housing. And of course, only do this on a cold engine.
Careful with the two bolts on the thermostat housing as they screw into the aluminum intake.