This just started on my 95 F-150 XLT 6cyc 5 spd. Seems like when I accelerate hard the a/c air cycles (while on high/max) from the front vents to blowing out the defrost vents. After let off of the accelerator the air cycles back to the front dash vents.

I noticed that the same thing started happening with my ex's 95 T-Bird; however, at the time we just split up so I never worried about it....

Anyone have any ideas?

 

Sounds like a check valve in one of the vacuum lines has gone bad.

 

When I looked at the check valve on the hoses that come from the reserve tank (coffee can looking thing) I saw that one of the hoses were not fully pushed onto the outlit of the tank. That appears to have fixed the issue.

Thanks for the help