The A/C stops blowing duing acceleration on a slight grade at highway speeds.

FRANKHG

MEMBER
2000 FORD E-SERIES VAN
11,000 MILES

I appear to have a vacuum leak causing the A/C to shut off on slight grade accelaration. Had the hose leading to the vacuum can replaced as it was rotted, but does not solve problem. Where should we look next?

It works fine for the most part unless I am travelling up a very slight grade at speed, but not yet downshifting. Additional problem may be related and that is the cruise control often has difficulty engaging. I think it is also vacuum controlled is it not?

1 Reply

WRENCHTECH

MECHANIC
20,761 POSTS

The mode selection is done through a series of air doors that are operated by vacuum. When there is either a partial or total loss of vacuum, the system will default to either defrost or on some vehicles, heat. Acceleration can also have an effect on the doors for the same reason.

Look under the hood for a small black plastic hose coming through the firewall. Follow it to the vacuum source looking for any breaks, cracks or leaks. Also follow any other lines that branch off because they may go to a vacuum reservoir (storage tank) and a leak there will cause the same problem. Using a vacuum gauge to determine if you have full vacuum at any given point is the best way to find it. You can cut into the line anywhere and splice it back together with a piece of vacuum hose. Find the broken line, you found your problem.