We run Western plows and follow their trouble shooting guide. They are not too complicated if you are somewhat mechanical. I usually will find myself following the guide step by step to isolate the problem. I also seem to recall from helping a friend who runs Boss plows that wires behind the plug in connection on the truck corrodes and break off rather easily.
Here's a Boss trouble shooting guide:
http://service.bossplow.com/database...ting_guide.pdf