I've have problems with corrosion on the plug connection between the co pilot and the power drive unit. If you have one of those little wire brush things for cleaning your trailer connection plug, you can use it to clean up the pins some. The holes in the socket part are too small to get a brush in. There's probably some kind of spray cleaner you could use, but I don't know of any myself. Sometimes just working the plug in and out a half dozen times or 2 will get it going.