Looking at the KW website, the OD relay pictured won't work properly with your system. You need the one pictured in Terry's reply which should resemble what was on your car. About rebuilding, the top of yours can be removed and will reveal a set of what looks like points. Typically, they get scored from years of use and stop making clean enough contact to work properly. The contacts can be cleaned with light sandpaper, I use 400 grit wet or dry (dry) to dress them. It's worth a try.