Class A Gasoline motorhomes have NO auto AC shut off. AS others mentioned, the Aftermarket Dash AC systems on motorhomes are Vacuum hogs. They have leaks and on heavy acceleration, when the engine vacuum goes to 0, the Dash AC blend door motors use up all the vacuum including in the vacuum reservoir. Adding a larger or extra reservoir rarely fixes the problem. The best result if you are always in hill climbing or lots of times you are driving at high speeds and lose vacuum, you install the same 12 volt vacuum pump the Diesel chassis's use. That way you will always have the needed vacuum. The AC is NOT shutting OFF, the Compressor and fan motor is still running, the air just comes out the defroster vents. Once the vacuum is restored the blend doors close and the air then comes out the dash AC vents. Doug
