Find a qualified repairman and if you take the job on make sure you have and the correct schematics showing how the components are hooked up. Generally faulty wiring can be repaired providing you have the proper tools such wire, solder, switches, screw drivers, nut drivers, contact cleaning solutions and soldering iron to name a few. Simple wiring or soldering jobs can be done by a local TV-radio repair shop. They have access to the materials for repairing the instrument and I've found they enjoy working on guitars after long hours working on appliances. Many times the problem can be caused from corrosion or cold solder joints that have oxidized. With a good eye and an volt/ohm meter you can easily repair many of the problems.