Hey ya'll, hope all is well with everyone! My heat issue awhile back WAS my actuator for the blend door (hot/cold).... the biggest gear inside actuator had 3 different fractures, and the motor mount inside was also cracked...... went too pick n pull and was able to find another, didn't want to spend 150$ for new

 

What other diagnostics have you done? Is your coolant level full? Have you replaced the thermostat?

 

BTW: What year and what type of climate control; manual or "computer controlled" with temperature set-point?

You can find the actuators for much less than $150. If you got an old one from a wrecking yard, it is not unlikely that it broke too after you started using it as it was just as old as your original one.

I'd check if it is still working correctly.

 

Are you reporting your successful fix or are you still trying to figure it out?

George

 

So, mine tends to work when it wants to. (98 LT with electronic HVAC) Worked fine until I replaced the fuel pressure regulator, and since I was in there I threw a 160 degree thermostat in too. the heat stopped working after 5-30 minutes each time I drove it, so I decided to try and bleed the system, there was a lot of air in it, but after a day of it working the same thing happens, It will heat great then switch to cool air after a while. I dont hear any sounds in the dash when it happens, it just switches. And sometimes if I shut the whole truck off and wait a few minutes, and restart it, it works fine again. So I was wondering if there is a sensor or relay or something that I didnt know about that also controls the temperature? This has been the most frustrating Blazer Ive ever owned,LOL.

 

From what I understand, these 4.3L engines in our blazers require the 195* thermostat. I don't know if that has anything to do with your heater problem, but the coolant temp sensor reads the 195* for the engine computer system to work properly. Maybe someone else could chime in on this.

 

It finally kicked all the air out of the system, after bleeding it at least a half dozen times. The heat works great now. Now, on to the next problem. 😆

 

Yeah! Thanks for the update. It is good to learn that air in the system can cause this.