[Camperman]

It sounds like you may have a bad ground. IF it is corroded it could make contact but will reduce the electrical flow to the motor. I would remove all the contact points and either clean them well or solder new contact points. I had a similar problem recently with my coach not starting and had to use the aux. power. I had 3 RV dealers look at it and spent serious money but no one found the problem. I took it to my local car mechanic and after half an hour he found that the power was low. When we removed the battery cable there was lots of corrosion. We cleaned that off , cut off the connector and attached a new one. We filled it with solder and dipped the wire in. There will be no more corrosion there. I had the same issues with my electrical step. Once the ground was replaced the problem was solved. I had to replace several switches also due to corrosion, all because I didn't go South last winter but stayed in the snowy North.