The A/C on my 84 still blows cold but it only comes out of the top of the dash and not the regular A/C vents!!! Because of this it doesn't cool my car very well since it's just blowing onto a hot windshield.

I'm assuming that the tiny vacuum hoses behind the A/C controls that controls which vents open and close with what setting are falling apart with age and that those are the problem. Does this sound likely?

 

make sure the vacumn supply line connected to the engine is still connected and not broken/clogged

 

I've got the same problem, anyone know where in the engine bay that vacuum line is supposed to be at? I no doubt busted mine off at the firewall or something or just missed it when I swapped engines....

 

Occasionally I have the same problem, not all of the time though. Sometimes when it does it I move the selector to all the choices and eventually it starts to work.

 

well that's a very scientific and methodical way of doing it

i'm jk ... it seems like if you monkey with and beat any modern appliance (besides a computer) it'll kick back into gear

 

Im just trying to say that the problem could be in the selector switch as well, maybe some kine of internal leak.

 

I fought the problem for months. On a I've-got-nothing-better-to-do afternoon, I swapped out the selector switch. End of problem.

JamesC

 

hmm.. yeah I just got this same problem also.

 

I was told long ago that one of the vacuum hoses is being pinched and not holding vacuum. That would cause it to blow out the defroster vent.

 

So can someone post a pic or a diagram of where the vacuum hose goes through the firewall and where it connects to the engine so I can try that first. I kinda don't want to replace the entire assembly, it looks fine

Thanks!

 

These "cables" are actually small plastic vacuum lines from the A/C controls which actuate small vacuum "motors" underneath the dashboard next to the firewall (they look like small silver tops with a small color hose attached to them). If you pull out the A/C control panel, you will see different colors corresponding to a control setting - blue for defrost, orange for floor heat and so on. The "motor" moves the control gates for directing the airflow via the dash and console vents and so on. The usual problem is that the vacuum source line gets broken or pinched from the vacuum box (on the firewall next to the washer assembly) to the controls. When the vacuum source is interrupted, the controls freeze on the last setting of vent, defrost, etc since there is no vacuum source to actuate the "motors". Follow the main vacuum line (usually a stiff black plastic line) from the box to the original vacuum source (A/C system or manifold) or from the box to where it enters through the firewall to your control switch to see if either one is broken or pinched. This is what you hope is the source of the problem.

Next, check your vacuum line to see how it connects to the harness with the color coded lines (see the Chilton repair manual for the difference between early and later f-body a/c system controls). If any line is broken, it is usually another potential vacuum leak as it is all one piece. This can happen when installing a new stereo system as everything can get jammed up behind the console. These can be repaired by splicing in 3/8th inch rubber hose. The problem you don't want is a broken connection at the control panel. Since it is a one piece vacuum harness, it can mean removing almost the entire dash, seats, hope this helped a bit guys

 

I once had this problem, it was the vaccum line that runs to this Black Bowl on front passenger side. Look underneath the vehicle for the vaccum line and ensure that its connected. They are very easy to come loose. Do this before replacing different items. That Vaccum line pull the air into the vents of the car..
"TRUST ME BEEN THERE DONE THAT"

 

I think that is what 92GTA (and myself, incidentally) are looking for. Emphasis on the LOOKING part. I have the same problem with my vents. I checked the hoses when I replaced the stereo (vent problem was pre-existing) and they looked fine. The vacumn canister on the firewall, however, is missing one of the hoses, and I don't know where it runs from/to. The hose going from the firewall to the canister is there, it is the other one that is missing.

 

Get under the car, driver side front end (Just to the left of the radiator hose you will see this black moon shape canister about the size of a minature basketball. Here you should see a vaccum line running to this canister. If its missing or came off just plug it up and you are good to go. Once again you have to get under the car and locate the canister.... If you cannot find it I will take a picture tomorrow and post it, just let me now.

 

Just so I understand this correctly.... The line from this "half-moon shaped canister" under the car runs to the vacumn canister located on the firewall? Just want to be clear before I go crawling around under the car.

 

so thats what thats for that canister..i hope that solves his problem i have the same problem but only when i select the "heat " setting it blows from the defrost only..update us vampire