Ok now, I feel like a dummy and need to figure this one out. I have a 2004 Chevy Blazer and no heat coming from the vents, have proper air flow and am able to get air on all settings. I have read some of the postings on here and haven't figured it out yet. I checked the heater hoses they are look warm. So I am assuming that there is no circulation through the heater core. I am not able to find anything from the chiltons book. Can anyone help me? I need to fix this today..........thanks Gary

 

With it hot or at operating temp, can you feel hot top hose flowing?

 

there is a good possibility its the heater blend door/actuator. turn on heater. switch it to the cold temp, then switch it to hottest temp, listen for a change in the air speed/sound from vents. if no sound or change, it's likely the door that switches from hot to cold is not moving. could be stuck or the motor that moves it has gone out.

 

as far as the cooling system yes, as far as the heater core no.

 

the blend door is working properly, i checked all of those, when i switch the temp switch around i can hear some vacuum action and can feel lukewarm air. All of this started when i changed out the thermostat. i dont see any place that could affect any vacuum lines and what not.

 

what temp thermostat did you use? also, is the blend door switching all the way?

 

i used oem thermostat, went on ahead replaced the actuator havent checked yet to see for sure if it is switching. i will look at that tomorrow to be sure. I also don't know if i am getting circulation as well through the core as the heater hoses aren't even hot. so i am more confused now than ever...........ugh........lol................G

 

Is there any valves in the heater hoses before it goes in the firewall?

 

none, i am goin nuckin futs over this dang thing lol......... i pulled the hoses tonight and have flow. its got to be inside of the distribution housing is all i can think.

 

grungyrider Welcome to the forum
from what I have read of your post and others I think you might be on the right track with suspecting the heater core...if the heater hoses are only lukewarm with engine at temp then I to suspect blockage....
The heater core runs at engine temp and the temp is controlled by how much or little cool air is allowed to flow over it...