Allow me to rephrase the A/C question

[Motorhead350]

A fellow member told me I was not completely clear on the issue with E-250 and the A/C. What happens is the A/C will stop blowing air though the vents at half throttle or greater.

You still hear the fan working, but it seems to blow out the windshield and stay cold. This seems to be the defrost mode someone else was talking about. The air doesn't stop being cold at WOT, it simply quits flowing out of the vents until I am lighter on the throttle.

Is this normal? Like I said, it doesn't take WOT to stop air flow, it's about half throttle or greater.

Sorry if this is a repeat. I could not find anything wrong when I took apart the controls in the interior.

[fastblackmerc]

A fellow member told me I was not completely clear on the issue with E-250 and the A/C. What happens is the A/C will stop blowing air though the vents at half throttle or greater.

You still hear the fan working, but it seems to blow out the windshield and stay cold. This seems to be the defrost mode someone else was talking about. The air doesn't stop being cold at WOT, it simply quits flowing out of the vents until I am lighter on the throttle.

Is this normal? Like I said, it doesn't take WOT to stop air flow, it's about half throttle or greater.

Sorry if this is a repeat. I could not find anything wrong when I took apart the controls in the interior.
Not normal.

If the air comes out the defrost it's a symptom of low vacuum. Since the van is old I'd check all the vacuum lines and the vacuum tank for leaks.

[EMAS]

That is what happens when you have a vacuum leak and/or a bad check valve in the system, if there is a check valve on that model. The vacuum motors are spring loaded, when they have no or low vacuum they return to a default position. The default position is full defrost.

The vacuum leak could be in the hose that runs into the cab, the reservoir, the control head, the hoses between the control and vacuum motors or the vacuum motor itself. You just have to trace all of the system until you find the leak.

[gpfarrell]

I'll bet you can find an answer on ford-trucks.com . It sounds like a bad check valve to me. The van would run like crap if you had a major vacuum leak, so I doubt you do. Probably a $10 fix if you can reach the part under the dash/dog house.

[Motorhead350]

It runs like a champ. Dependable as rust. I will check on this check valve in a few days.

[EMAS]

It's not a major vacuum leak that causes this problem it is a small one and it will cause this problem with a good check valve.

[8UWITH6]

Check the vacuum lines coming through the firewall to the hvac control head. This is probably where your problem lies. Good luck.