Ford 15 pax van w/V-10 and AC issue

Hi,

I had a 94 work truck that would ping when the A/C was on "Max AC" while going up a hill. This is because there was a vacuum leak in the outside air door.

You might try running normal A/C and then know that if you do decide to use Max AC while going up hills, you need to fix the vacuum leak in the door (about $200 - $400 in shop time) before the system will work right. However if it works on regular A/C under full throttle applications, then all will be well, even if not fixed.

You are still getting cool air, just it will be coming out the defroster vents. This indicates a vacuum leak someplace. Very easy to fix, once you know the location of the leak. It might take a hour or so of shop time (normally about $90+ per hour) to figure out the leak location.

There should be a check valve so that the system continues to get vacuum while at full throttle. It might be leaking, and installing a small vacuum reservoir would also help, it will look like a round ball or something the size of a coffee can with a vacuum port on it.

You can also just let off the throttle for a couple of seconds, get the vacuum level back up, dash vents will open again, and continue on your way up the hill.

Good Luck,

Fred.

loss of vacum for sure had the same problem in my 97 15 pass last summer

Could be check valve, vacuum line or crack in vacuum reservoir. Usually its the check valve.

Put your hand over the defrost vent the next time it quits blowing out the vents, then follow up with what the ^ fellars said

Yup. Vacuum leak for sure. Possibly a check valve if it only does that up front.

In my case, the rear selector door vacuum actuator ruptured. I don't think that is common though. Usually its an elbow that came loose under the hood, or sometimes rodent damage.

Are you sure it's just not that the air switches to the defrost vents when pulling hills? Because Ford's have had an issue with vacuum driven controls where they will switch to defrost (still cold air) when under heavy load. Generally this is caused by a leaky vacuum line or reservoir.