a/c blows out from defrost and floor vent 86 monte carlo

[RO86SS]

a/c blows out from defrost and floor vent in my 86 monte carlos...does any body know what it might be...

 

[breeaad]

a/c blows out from defrost and floor vent in my 86 monte carlos...does any body know what it might be...

The vent doors in your dash are operated by vacuum. You most likely have a vacuum leak. If I were you I would pull the heater control panel out of the dash and look for a loose or broken vacuum line.

 

[flip66]

check the purple vacuum line by the AC under the hood.

 

[85 Cutlass Brougham]

If it is not the vacuum line under the hood, it is probably the vacuum switch in the HVAC switch assembly that has failed. If you can hear hissing from the dash all the time, the switch is bad.

 

[mugzi]

if the vacum lines is messed up under the hood does anyone know how they go. i'm having the same problem

 

[85 Cutlass Brougham]

You will want to route the HVAC lines like this: Gray line runs the heater valve. The purple line runs the vent doors. The purple line uses manifold vacuum which goes to a check valve and then to the vacuum storage canister then to the purple line which runs to the dash switch. The check valve keeps the canister from losing vacuum under hard acceleration which would make the doors switch positions back and forth. The canister therefore acts as a buffer in the system to maintain vacuum under a variety of conditions.