[MrArachnid]

I have recently been having a problem with my A/C. I am hoping someone can give me a clue as to the nature of this. My A/C blows cold but the venting switches from the cabin vents to the defrost vents on acceleration. It does this anytime I accelerate. If I let off the accelerator the A/C starts blowing out of the main cabin vents. I am stumped as to why it would act like this. I am hoping to avoid tearing into the dash. It is like there is a power issue. I recently did a tune-up but it was doing this before the tune up. I have a 1993 2.3L.

Anyone have any opinions?

[flash-1295]

There is a vaccum line that runs across the rear of the engine bay (firewall) near the top. It runs from the drivers side to the passenger side and into the firewall behind your glove box. If you lose vaccum to your A/C the unit will only blow out of the defroster. That could possibly be your problem. Could be loose or kinked hose or small leak. Worth checking anyway.

[krk105]

The actuator for the vents is controlled by vacuum. The vacuum is created by the engine via the intake. Thus more acceleration creates more vacuum. The increase in vacuum is causing the actuator to move. So........why is the actuator vacuum pressure changing when it should stay constant? this could be caused by a faulty switch on the control panel or a vacuum leak in the system.

[Mac The Knife]

Flash is close,,, I had the same problem with my 89 lx,,, but the line doesn't just go into the fire wall, it goes to a combination checkvalve tee assembly, with one going to the heater controls and the other going inside the passenger side fender, where Ford hid the vacuum cannister. My problem was that the vacuum cannister was not hooked up, and the checkvalve wasn't sealing. I made up a vacuum cannister, and flushed out the check valve, and all was good,,,, here is a link to a vacuum diagram for the 2.3 http://www.allfordmustangs.com/forum...um-diagram.png