Let me start out by telling you what car I have, just incase that makes a difference. Its a 89 Formula 350 TPI. Ok The problem is ...The heat comes on in the car but only in the form of the windshield defroster on the top of the dash board. Doesnt matter what I switch it to, it wont come out of anywhere else. It just stays on that. I can the **** to make it blow out harder and that works fine and so does the slider that controls how hot or cold. For some reason though I cant get it to come out of the vents facing you or by your feet no matter where that top slider is moved. Its been like that for quite some time and I have ignored it, but lately the fan for the heater goes higher as if I turned the **** up when I didnt even tuch it at all. This just started happening and it only does that for like a second or two. Hopefully I have explained this well enough for everyone to understand. Any and all help is greatly appreciated. Thanks.

 

The air doors are vacuum operated. The default (no vacuum) is defrost. The vacuum line is hard plastic and enters the engine compartment (through the firewall) with a wire bundle near the passenger side head (at least on my car). Check for vacuum there.

 

Yeah sounds like a vacuum issue. Unfortunately it could be a real pain to locate because like he said the vacuum lines come through the firewall to your heater controls which means they are mostly behind the dash. While you've got your dash apart make sure the heater door will open and close freely. Good luck.

 

This will probally wait until a day that Im fealing really adventurous. I had the dash apart once to change the cluster and it wasnt fun. Not hard just took me awhile. I dont feel lioke going through all of that again. It comes out through the top vents for know and still heats up the car fine while defrosting the window. Honestly, I wish I asked about this in the summer. The real problem is I just moved into a new place with my fiance out of my dads house and I dont have a garage and its December in NY. I dont feel like being out in the cold weather unless its something thats really important or a quick fix. Thanks alot guys. atleast I know where to start whenever I do get into it.

 

I just had the same exact problem and it turned out to be the vacuum line was melted on the passenger side of the engine compartment right above the valve cover .

 

I've got the same problem on my '92 firebird is it in a different location, or is it on the passenger side near the bundle that runs to the power antenna and such?

 

nathan I'm not sure if it's in the same spot on mine it's one of those hard plastic lines not a regular vacuum line if that helps you narrow it down.

 

Thanks it dose give me a place to start which is more than I had before

 

I have a similar situation. I have a 92 rs 3.1. The heater cores and all the cooling system is new. motor heats up fine but i still get no heat. the vacuum hose going to the diverter valve has no suction. The shop i took it to said i need a new head unit and that should fix it. I ordered one but i still feel like its going to be what yall had, the vacuum hose melted or broke. What do yall think?

 

My '86 Bird's vacuum line starts near the brake booster and is fed/sucked from the intake manifold.