Ok, my a/c would only work on one setting. It only came out of defrost. I found a brittle and broken vacuum line under the hood. I cut and spliced it back together and my a/c, heat, and defrost all work as they are supposed to. NOW when I’m driving and I change speeds, slow down, you hear a thump and hot air comes out a/c vents. I know it's a door under dash, but which? Is it the door operated by switch shown in picture, or another? How to fix?

 

What are you driving? On the older second gens, the temp door is controlled with a cable, on later trucks, there is an electronic controller, vacuum is not involved. Blend doors like to break though......

 

1999 Dodge Ram 1500 5.2

 

OK. You have the electric blend door. There is a coupler between the motor, and the axle for the door, that likes to break..... HeaterTreater.net has the fix. Start there.

 

if the door you are talking about is the door controlled by the switch I have pictured I’m confused. I can turn the switch to the hot side and it does get hot and if I turn it to cold it does get cold, so the actuator does work. But I can’t pot it in middle to turn heat down, it either goes all the way to hot or to cold depending on which way I’ve got it turned.it’s like the motor keeps turning. Actuator faulty?
Also, it doesn’t act up unless I remove foot from accelerator and slow down. That’s what gave me idea of vacuum issue. Lol, this has this old brain all confused.

 

Ok, I may know the problem. When I first got the truck I couldn’t get it to go from hot to cold. I took the blend door actuator off and I still couldn’t get the door to open. It was stuck from Im guessing sitting for so long. I had to force the door open, then the actuator worked but it wouldn’t stop at mid settings, it goes all the way to cold or hot depending which way you turn ****. Something stripped?

 

The coupler is likely broken, as that is VERY common, the blend door also likes to break off from the axle.... Given your symptoms, I *think* it's just the coupler that's bad. You will likely need to re-index the actuator motor as well.... Heater treater has all the instructions for just such an occasion.

 

I FOUND THE PROBLEM,thanks to you! I’llt looks as if the previous owner tried to fix this by trying to clamp it. I have the part ordered from Heater Treater.

 

Yep yep. Standard problem there. Creative attempt at a fix though.

 

ok the problem is FIXED! But get ready to laugh your *** off! The little motor fell out of the case and I guess I put it in backwards. When I turn dial to hot it goes to cold. If I turn it to co log d it goes too hot. Not a hard fix, but not ready to crawl under dash. Lol at least it works!