Cab AC

[Bluesky46]

I have recently noticed my cab AC goes off when I’m going up a hill. I’m talking about the engine AC, not the AC on the roof. Maybe it’s supposed to be that way but I sure never noticed it before. As soon as I crest the hill it comes back on. Anyone else experience this? (2012 Greyhawk 31SS)

[Robbbyr]

Does it go warm but still come out of the dash registers? Or does the airflow seem to just stop flowing from the dash registers?

Fords A/C systems are vacuum operated, going up hills causes low vacuum and the system "fails" to the defrost mode. Does the air flow switch to the defrosters when you experience the problem? If it does, you may have a vacuum reservoir that has a leak or a bad vacuum check valve. Both not uncommon problems in older Fords.

If it is just the air getting warm but still flowing from the dash, Fords also have an A/C compressor cutout. When the engine is under high load it shuts off the A/C compressor so that all of the engine's power can be utilized to climb or accelerate. But most only cut out at full throttle. Are the hills so steep your are likely using full throttle?

[JmsNMar]

Hello. I had that exact same problem with an '05 Tioga on a Ford E450 chassis that we once owned. Took it to a local mechanic shop for repair, but the issue did not get resolved. I sold that RV to upgrade before actually fixing that issue, but if I had kept it, I probably would have bit the bullet and taken it to a Ford dealership to have them fix a problem. I, too, believe that is a vacuum issue, and the vacuum systems on those engines are very complicated. Good luck, and I hope you get that resolved. Happy Trails...