Are you trying to fix one of the really old ones that use a 6 volt dry
cell pack, or one like Harbor freight sells that is solar charge? The
really old ones used a 6 volt turn signal flasher to close the
circuit. Don't think they are legal in any state, now. I have one of
the Harbor Freight units that has a bad solar charging circuit. Never
had time to look at it. If this is what you have, would be very
interested in what you find is wrong with them.