what controls the ducts to be switched in the car for heat... there is only vacuum in 2 lines red.. purple.

 

The air doors in the plenum are controlled by vacuum and cables. The setup is different from year to year. The best bet is for you to get a Factory Service Manual. They should have the under dash vacuum diagrams.

 

you guys know if the valves can be replaced? or know any tricks for them to work

 

Air valves usually are a can with a diaphram connected to an arm. When they fail, the diaphram has split, cracked or otherwise won't respond to pressure differential. So, in a word no, they cannot be made to work. You will have to replace them if you are sure they aren't working. Make sure you have a good vacuum signal to them before doing so. You can even "steal" vacuum from a good manifold source, using a very long vacuum line and connect it directly onto the valve, it should actuate.

 

Tell us what year an model of car and we might be able to give you a useful answer.

 

80 cutlass calais