Buy the replacement unless your time is not worth any thing to you. I have done extensive work on the headlight switches and it is very labor intensive and requires special materials to repair. The entire unit is crimped and riveted together and is a sealed unit. If you don’t use extreme care in disassembling the unit you will probably destroy it. I have made special tooling to work on the AD switches for the purist but it has proven to be much cheaper just to replace them with the after market units.
It sounds like you probably have a burned dimmer rheostat or corrosion at the copper rivets and possibly damaged contacts inside the sealed switch unit itself.
Here are a bunch of pictures of what you are getting your self in for if you decide to attempt the repair. Dimmer: http://rides.webshots.com/photo/2190351730098611668cFmtBO
Switch Assembly: http://rides.webshots.com/photo/2771340540098611668Fshdxs

Denny Graham
Sandwich, IL


Denny G
Sandwich, IL