There is this black plastic tube coming out of the fire wall on the pass. side if the car. My A/C blows out the defrost vents and that tube is not hooked to anything, just hanging there. Can anyone tell me what it might be? Thanks

 

That is a drain for the A/C system. Just like a cold glass of water gets moisture on the outside of the glass and this can run down the glass onto your table, same thing with a cold A/C unit. It accumulates water. And this water needs somewhere to drain.

That inside section of coils which gets cold is called the "evaporator".

 

I believe you are talking about the vacuum line for vent control. The defroster vent is the default position if there is a vacuum loss. There should be a vacuum reservoir that is connected to manifold vacuum (a small canister or ball depending on what year your car is), then the vent control line is connected to the reservoir.

 

Would you happen to have a picture I can see, I really want a/c in florida.....I have an 86 T/A with a carb (no computer) 305...There is a round canister under the front bumper, and a square one by the driver side headlight. Do I need a check valve also? Thanks for yalls help....

 

Vac line should run from intake through check valve and split /or split at check valve as shown in pic .One line goes inside to operate your A/c controls and the other goes to the vac ball.This keeps your vac supply for when the vac drops like when you accelerate.

Pic from a TPI car but yours should have similar.