Heater Problem

Well I seem to be having a bit of a heater problem in my 2000 Blazer LS. At first, my heater was only blowing semi-warm air. My coolant was looking a bit low, so I topped it of and replaced my thermostat today. Now the heat blows hot, but only when I'm moving. At idle, it still blows only semi-warm. Anyone know what the problem may be? Thanks.

That's the sign of low coolant in the radiator, You may have air in the system and just need to purge the air out of it. Every morning you need to check the radiator and top it off when it's cold till all the air is out...

Also considering it's dex-crap (dex-cool) I would back flush the heater core as well incase it may be sludged up a little bit. Change your oem cap to a stant cap and it will bleed the air out better.

Well I seem to be having a bit of a heater problem in my 2000 Blazer LS. At first, my heater was only blowing semi-warm air. My coolant was looking a bit low, so I topped it of and replaced my thermostat today. Now the heat blows hot, but only when I'm moving. At idle, it still blows only semi-warm. Anyone know what the problem may be? Thanks.



Hey i had that exact problem 5 days before my water pump went out, also accompying the heat issue was a damned water sloshing noise when i got on the throttle. Check for coolant leaks and that noise as well. I assume the leak allows air in the system and the low coolant doesnt help.


(Coolant issues used to be the #1 problem with my beast. Started with the water pump, replaced thermostat early ((take that blazer)) than the upper and lower lines, than the cap leak than at last the heater core. Oh crap sorry to scare you. i was venting.)

I want to state that it may just be low coolant, my issue may be isolated. The low coolant was because my water pump was leaking and causing air in the system, so yeah go with what dino55 said and check the level