Is there someone out there that is smarter/more experienced in these things then me that can answer this? So the wife's blazer has had very little Luke warm air. The core is flushed and flowing, there are no vacuum leaks that I can find or hear, and the blend door actuator has been replaced. The vacuum actuator seen sitting disconnected was preventing the blend door (the small white hook in the shadow to the right of the bronze bolt on the left)from going hot it would barely move. Once it was unhooked the blend door moved freely and went hot. Once it was removed the diaphram moves in and out not problem, but when you hold you finger over the vacuum line tube it will barely move. Temp control goes hot or cold now without it attached so what does this diaphragm do and is it needed?

 

Does the Blazer have manual or auto HVAC? And what year is it?

 

I'm no expert, but just went through all of mine yesterday and fixed my heat issue. I used a Mighty Vac, vac pump (like $25 at local auto store) to connect to the actuators individually to verify which ones worked and didn't. It sounds as if you already found the culprit actuator, now you just need to see if a supplied vac source will operate it. You need to manually apply vac to it; does it operate as advertised? If not, replace actuator, if it does then you have a vac problem. Does the selector work (vent/floor/defrost)? If it does then you would eliminate the typical vac hose problem.

You could also test the vac source, disconnect line and connect a vac gauge to the line and see what the supplied vac is, if there is any... Both tools were cheap and made my job so much easier yesterday, now everything works on mine. Good luck!

 

Sorry I should have noted its a 1999 with manual heat. I am really curious. If the blend door is electronic and moving properly why would it have a vacuum acctuator and what would it do. I am befuddled.

 

Check out this post to include the schematic... https://blazerforum.com/forum/2nd-ge...l-issue-69344/

It should help answer some questions.

 

TY Mag! If I am reading it right it's the actuator for the fresh air/in car air door. Kinda makes sense since AC/cold/defrost prob looks for cold outside air as a default. OK I can kinda see that now. Ty again

 

If your finger is sealing off the actuator's vacuum inlet, then no the diaphram is not going to move if the diaphram is intact...no where for the air to go.

So was there an interference that was keeping the blend door from moving? If so, then something is either bent or broken as there should be no interference of course. I think there are videos on youtube that show this area that you can view to help determine what is wrong.