If you plan on trying to repair it yourself, call Lippertand they will walk you through the diagnosis. If it's under warranty the dealer can call Lippert for assistance.
I have a Montana with 4 slides that was doing the same thing. The dealer tried to repair without contacting Lippert and ended up replacing the valve body, the control Body, and outside switch panel, none of which worked. They had my camper for nearly 4 months before they finally called Lippert. The techs at Lippert told them how to test the Hydraulic Rams and they found 2 that were leaking past the seals, no external leak, after getting 2 new Rams the problem was solved. I've had no problems since.
