I have an 86 cutlass that only blows out of the defrost and floor vents. I can't get it to blow out of the dash vents and it always blows on both defrost and floor. Anybody know anything about this, or where the selector door is that controls this.

 

Bad vacuum diaphragm, hose, or controller to the mode door that switches between A/C and heat.

Check your manual for line colors, controller ports, and location of the diaphragm, then apply vacuum at the appropriate points to figure out where the problem lies.

- Eric

 

X2
I had the same problem. Mine ended up being the controller. This also came up once before. You might also want to check and see if the plastic tab where the pushrod goes is broken and the pushrod may have fallen off/out? That would prevent the door from moving.

 

If vacuum to the system is lost, this is the default condition. Carefully check all vacuum lines and connections to the HVAC system. My money is on the vacuum connections.

 

Good point, Joe. I couldn't see the forest for the trees.

No vacuum at all (line disconnected at the engine or the reservoir) will give the same symptoms he's got.

- Eric

 

Ok so where would the selector door be?

 

I have no idea where it would be in your car - probably in the center, up under the dash - that's why I suggested you check the manual.

As Joe pointed out, though, you would get the same symptoms from no vacuum supply at all, so you should check your vacuum lines from the engine first.

- Eric

 

The hard plastic lines break easily after becoming brittle through age and heat.
Here are the manula pages and a picture of mine.
Check the black and violet lines (LEFT side of vacuum tank in left of pic) and their rubber connectors first...