So my blazer has always a funky problem with the Ac and heater. For a while there I thought the Ac was dead because it only blew hot. Then it it would blow cold. Well I didn't care that moving the temperature wasn't working when it was the summer but now that it's starting to get cold in the morning I would like to adjust the temp between hot and cold. So I read online common problems and it led me to believe my blend door actuator was getting stuck on either hot or cold. So I replaced it just now and it didn't change anything. I can see the door moving when I turn the dial but nothing changes in the temp of the air.

Only problem I've ever face like this was because I by passed the heater core on my mustang before but nothing is bypassed on the blazer so I'm confused what to check next. Thanks guys

 

flush your system disconnect the heater hoses at the fire wall flush out with air then put some clr into one of those outlets let it sit for 5mis flush with water and again with air refill system should have heat p.s. it will splash when you flush with the air so cover the engine or have someone hold some rags near the other outlet

 

Thanks. I did this earlier today and it seemed to fix the problem. Time will tell when it really gets cold. A few dry looking rust flakes came out. No goo like I was expecting reading other threads. But it's working so I'll take it.

Edit: I didn't use CLR just sprayed it out with air. But I do plan on cleaning it more when I have more free time

 

I would recommend using the clr you will be amazed at what comes out, did mine 3 years ago I still get heat like a new vehicle and the a/c seems colder

 

Flushing the heater core has zero impact on the AC air temp....totally different system.

blazer 512: when you replaced the blend door actuator, did you by chance rotate the blend door manually to check if there was any binding going-on?

When using compressed air to blow through the heater core...be easy on the air pressure; high pressure could blow out the core and then you would get the delightful task of replacing the heater core.

 

I did this 2 years ago and the water that came out was black. Now I have excellent heat.

 

I will do this my next day off. seems pretty simple and quick

Thanks for the tip with the air compressor, have a suggestion on what to set the regulator at? I think i had it at 60psi. I didn't check the binding. To be honest, I believe the blend door might not have been broken or at least the time of removal bc i put the old one back in to maneuver the door into the correct position for the new actuator and it was turning find. But early this summer it would not blow cold, just cool/warm air so i'm thinking the door gets stuck? either way I'm not busting my knuckles to put the old one back in. its replaced.

Good to hear it from a second person. Means its definitely a great fix. Appreciate it!

 

Just did the flush and wow. I had heat at the intial start up. Not great heat but I could feel it. Once the engine got warm it's unbearable to sit in. I haven't felt heat like this in years. Thanks again for the tip.

 

I just did this on my mother in law's buick. Now the heat will run you out of the car.

 

Good to know. Maybe this will help mine as well. Heat works pretty good when turned all the way up, but if I adjust the temp **** down a little, it just blows cool air.