Ford AC Trouble


I have a 99 Ford Ranger 4 Cylinder truck. I have about 127,000 miles on it. When I have the ac on Max AC, anytime I press on the gas pedal, the ac quits blowing out of the dash vents and starts blowing out of the defroster vents on top on the dash. Also, when I have the switch in the off position, it will blow out of the floor vents. Now, it doesn’t do this when the switch is just on regular ac. The mechanic I took it to said he thought it was a vapor leak but couldn’t find it. What can I do or should I just live with it on regular ac?

Thanks in advance.



Vacuum leak at the switch/control assembly, or in the lines running to the air door motors.