AC and Heat only coming from defroster

I have a 95 mustang gt convertible. The ac and heat were working fine one day, then suddenly they started coming only from the defroster vents. nothing coming from floor or dash. is this a mechanical switch that controls the ducts or is it vacuum?

When control vacuum is lost to the vent system, it defaults to the defrost mode. So there’s a vacuum leak somewhere.


thanks. is this something i can check myself or does it need to go into a shop?

The first place to check is the vacuum reserve canister. This can be located under the hood, or behind the right front fender. It’s a round plastic ball. There’s two vacuum hoses to this canister. One from the engine with a check valve for supply vacuum, and one from the canister to the vent control system. Check these hoses and connections. If these check out okay, then it’s time to dive under the dash to locate the leak.


Does this car have manual controls (knobs that you turn) or EATC (digital display)? If EATC, it could be the control. There is probably a way to do a self test of the control unit. Ask on a Mustang board. If manual control, a vac leak is most likely and Tester has good advice. If you are looking for a leak under the dash, it could be in a vacuum line or in one of the vacuum motors. The recirculate motor as well as the ones that divert the air flow to the dash and other vents could be at fault. Your best bet under the dash would be to listen for a hisssssss. I hope that you don’t have loud aftermarket mufflers on this GT.