the heater/ac only blows through the defroster on my 91 rs vert. is there anything i can do to fix this, or do i have to buy a new one? any idea what's causing this? thank you.

 

Sounds like a vacuum problem. Either the switch diaphragm in the lever cluster is falling apart, or one of those capillary vac tubes is disconnected or cracked. Also check out the connections on that check valve where the capillary line comes into the engine compartment on the firewall, make sure it's not disconnected or that the valve is sticking. That's about all I can think of.

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DR Stevens
1984 Trans Am 305HO L69
sucks gas, hauls ***
1991 Firebird 305 LO3
for days when I need a/c

 

There's also a vacuum reserve 'ball' up under the battery. Sometimes they get cracked and leak.

 

Do you hear a leak at all near the A/C head (controls)? If you do, as mentioned before, you probably have either a cracked vacuum tube or most likely the rubbery manifold on the vacuum switch is not holding a seal anymore. It can be fixed without replacing anything by a couple of different ways. The easiest, I've heard, is by taking that manifold part off the switch and greasing the inside of each of the tubes with vaseline, using something like a Q-tip, or... if that doesn't work, you may have to separate each of those tubes and re-attach them individually... That's what I had to do, and the system works as advertised...

KAM