So its my sister in laws car who didnt want to bother me about her no heat issue. It gets pretty damn cold in CT in the winter here. It was pouring yesterday so I didnt mess with it for too long.

She was about a half gallon low on coolant (finding that source is another problem within itself) so I topped it off bled as much air out as possible. Truck does not overheat at all gauge read 210 and stayed there. The air coming out of the vents were cold not even slightly warm. The two hoses going into the heater core felt warmish. If I change the climate controls from HOT to COLD I can hear a change in the air going into the vents if that makes any sense.

Does this sound like its possibly just a slightly clogged heater core? (ive read ALOT of stories of plugged up heater cores on these blazers)
Is there any way to verify if the blend door is actually moving without taking out the actuator?
I cant think of any other reasons she wouldnt have heat

Crap I just realized I didnt grab the lower large hose going to the thermostat, but would it overheat if that was stuck closed?


Thanks all

 

Heater/HVAC issues on Blazers:

• Vacuum Leaks:
  • This affects to where the air is blown as vacuum is used to operate the actuators that open and close the valves for the air distribution.
  • From what you describe, this is not your problem.
• Lack of Heat: This could be due to one of two things;
  • no transfer of heat in the heater core which could be due to it being blocked or partially blocked, or because of air in the heater core.
  • The other cause of no heat can be to the blend-door actuator has broken. The failure mechanism for this is very often that the large gear in the electrically operator actuator has cracked and is no longer able to rotate the axle that goes through it and to the axle for the door.

For issues with the heater core, those will be remedied by proper flushing/back-flushing and refilling.

For the actuator, I think it can be checked by a couple methods.

• The first is to reach in through the glove box opening and try to feel if the axle for the blend-door actuator and the blend-door move when commanded by the HVAC controls. (There are plenty of videos on replacing the blend door actuator that can show you where to look.) I think this is how I first diagnosed my bad blend-door actuator.
• Another method for checking that also could provide a temporary fix is to remove an access panel that is on the top of the part of the heater box that is in the engine compartment. With this removed, you can see the blend door. If it doesn't move when commanded to do so, then the actuator is bad and needs to be replaced. I haven't done this but with the access door removed you might be able to manually move the door so that it is in the full-heat position. This will provide heat until a proper repair can be done.

Below are pictures:

The red circle shows the access panel removed. The green squiggle is the AC evaporator.



The red arrow points to the blend door and the yellow line is the axis on which it rotates. The blend door in this picture is in the full-heat position.

 

Does garden hose water pressure pass through the core at the fire wall hose barbs? Don't over do the pressure.

George

 

Thank you guys for help. I ended up flushing both ends after it appear clogged and we now have heat she is beyond grateful. We have well water and the pressure isn’t the greatest but it was enough to free up the blockage.

 

Whoo Hoo! Glad you got it fixed. And those easy fixes are so great!

 

Very good. Fixing your heat in January definitely doesn't suck.

George