It's always a good idea to make sure all electrical connections, especially the ones with large conductors, are clean and tight. I've never had a rig with a slide out, but every time I've had problems with a low voltage, high amperage system (hydraulic levelers, winches, dump beds, etc) it's almost always been caused by an iffy connection. It doesn't take much for a bad connection to break the circuit, especially in hot or cold weather. Best of all, it's a good early step because it's free and easy to do.