Ventilation Controls

[vmurh]

I had my heater core replaced in my 91 5.0 last November. I do not drive it that much and did not notice any problems except that the anti-freese smell was gone. Last weekend i noticed something while driving with short pants and no socks.

With the a/c controls on off and the temperature setting (the middle knob) straight up between hot and cold, i notice warm air coming out of the air ducts.

I then began to play with the controls and found that with the middle knob turned all the way to cold the air flow would stop. This does not seem correct. With the left hand knob on off no air should be moving i would think.

This past winter while driving with the heater on, my wife on the passeger side said her feet where cold. Maybe cold air may have been coming thru.

What does this sound like? Is it something i can fix. I hate taking the car back to the shop>

 

[ty-rone]

maybe the gasket between the firewall and the heater core. IF you don't have the gasket on air is going to squeeze throw the opening and through the dashboard. Also water can get in too and that's not good for anything.

 

[89MustangGX]

Sounds to me like one of the vents is not opening and closing -- most likely the outside one I think. There are vacuum tubes that lead to "canisters" that open and close vent doors to direct air. One is from the outside, one is for sending air to the vents, etc. It sounds like one of the doors is not doing it's job.

You may be able to find the loose tube by crawling under the dash and looking around. There is a chance it is at the connection on the back of the controls or another easy to reach connection ... the tubes sometimes pull out of their plastic holders and would cause this. You can try pushing them back in to be sure they are seated well (you will know what I mean when you get there). Unfortunately, having changed a heater core myself, if you don't see it right away, the dash will probably have to come down again to find it.

Good luck.

 

[vmurh]

Thanks.

I also noticed that the center temperature knob was harder to turn when i got the car back.

 

[89MustangGX]

Thanks.

I also noticed that the center temperature knob was harder to turn when i got the car back.

Definitely sounds like someone didn't take their time putting it back together. Fortunately, that's one you can probably fix by just movign the cable around until you find the sweet spot where it likes to route.