ac/heater

[1991cummins]

well, the other day my ac/heater suddenly it quit working completely, it still comes on every now and then but with no blowing force... i think it might be the control head just because either none of it works or all of it works minorly... what could have happened... is it possible a vaccum feed came loose or broke, or anything of the sort...

thanks,
Derek

[nooblet]

Yes its very possible. When i rebuilt my a/c system my vacuum lines where loose at the controls and at the coupler inside the dash. They were also loose at a few of the diaphragms.

Also check where the vacuum line from the pump goes through the firewall. It goes from the engine compartment to the cab right behind the glove box.

Other than vacuum lines I can't see how any 1 problem could make your whole system stop working.

Chris

[IRoss]

Check the wiring at your fan to see how many volts are going in there..just a thought..

[1991cummins]

what are those vacuum hoses made out of, should i periodically (every 17 years lol) change them? and would a weak vacuum cause a weak stream of air out of the vents?

[nooblet]

I don't know what they are made out of, but mine seemed to be very elastic still. Since they are inside the cab they really aren't exposed to that much in the way of sunlight, extreme hot/cold changes, etc... The things that usually kill rubber type materials.

My weak vacuum lines were causing functions to take a long time to change and not completely engaging. For example, it would take a long time from the "off" position to the "a/c" position (1-2 minutes). And some times the a/c position would never fully engage (half the air would be blowing out the heater vents and half were blowing out the a/c vents).

So to answer your question more directly... Yes, I think a vacuum leak could cause your problem. The vacuum diaphragms move a couple paddles inside the climate control box that can get stuck partially open/closed.

The fan controls are separate from the the vacuum lines though, so it could be those as well I would think.

Chris