A/C Issue

[jprisbe]

We have a '96 Firan Raven on a Ford F53 chassis.

A/C blows nice and cold... but every now and the it will suddenly stop blowing out through the dash and start blowing out through the defroster vents. After a short while it will switch back to blowing out through the dash again.

Any suggestions? Vacuum problem?

[John Wayne]

And I'll bet it does this when it is pulling a grade or hill. this is a common problem when you loose vacuum it goes to default mode which switches to the defrost mode. When vacuum returns it goes back to the dash vents. On mine there was a recall for a larger vacuum can and hose connection. You can add another vacuum can to help yours or down shift or slow down to build vacuum back up when it switches to the defrost mode.

[Lt46]

Yup, just as stated above.

[jprisbe]

I don't recall if I was pulling a grade at the time but I'll certainly take note next time it happens. Thanks for the info

[hdossett]

Had the same problem on even a slight incline on my '01, had the vac can changed out on a recall and under warranty @ 22,000 miles. On a '96 it might be a leak.

Harold

[garym114]

My 2000 spent two winters there in Alaska. On the way back to Texas the little vacuum pump got to where it would run all the time. I thought maybe the o'rings or seals for the pump didn't like the cold. When I got home I pulled the suction and discharge tubing to the pump and put a few drops of nail gun oil through it while it was running. It has worked like it should ever since.