A/C & Heater Vent Problem

[ERIC87442]

My problem is when i turn my blower on it only blows from the lower vents under the radio. it will not blow through the top vents on any setting. i pulled my heater control unit out and looked at things, every thing seems to be switching around and moving like it should, all the lines look okay and the lines under the hood are hooked up correctly. i do not have much experience in this department of the g-body cars so i could use a little help to guide me around with it. any ideas what to search for and what to look at or anyone else experience this problem?

 

[1984 Cutlass]

It usually ends up being one of those small plastic vacuum hoses getting broken or developing a crack. Check those out,they always get broken or moved during engine work.

 

[ERIC87442]

everything seemed to be okay line wise but maybe i just couldn't see it. I recently replaced the engine so maybe one of them are a cracked where i cant see i pushed and bent them out of the way to remove and install everything

if i remember correctly everything worked before i did the removal and installation of the engine. ill take a look and let you know what i come up with.

 

[ERIC87442]

well it has vacuum from up until the purple line for sure, i pulled the line off with it running and i could feel suction from it. so its got to be leaking somewhere else from the fire wall on in

 

[79CMC]

I had a similar issue and found it to be a stuck "trap-door" that directs air to the top vents-it's supposed to open when the car is running and the A/C is switched on (maybe it's just the fan that has to be on-I can't remember). I popped out the middle vents in the dash above the radio; should be two screws on either side and then you kind of wiggle them out-it's one piece in my 79 Monte. The "trap-door" is behind and below these vents and I used a flathead screwdriver to lift it up. I sprayed some white lithium grease on the hinges to keep it working for awhile.

It flows out of the middle very well now, but the side vents don't get a lot of air flow. I think I'm getting the best "stock" flow but I'm still interested in getting more air volume and colder temps as summer hits. Maybe I'll look at a vintage air system once I win the lottery...

 

[1LOW95GMC]

I also have this same problem. But my engine has not been removed before

 

[Bonnewagon]

I had the same problem but in winter I liked all the heat on the floor. But the AC does no good down there so I looked at it and found that even with the lower flap closed plenty of air went down instead of up. Everything looked to be otherwise working correctly, so I figured the flap was just not a tight fit. So in summer I roll up and jam a towel in the lower outlet, and ALL the AC air exits from the upper dash now.

 

[topstring]

Check your vaccum canister over by the heater box..when i swapped engines i cracked mine and bought a new one.