Plug in the guitar, place a volt meter across the tip and shaft of the cord, and measure the ohms!! Humbuckers are generally 8-12 ohms and Single Coils are 5-9 ohms. If you get no reading the pickup is dead or the internal wiring/switch or pots are shot. Diagnosing the problems is really easy if you have basic electrical knowledge and a few tools. There are a number of books available as well as web sites like Stewart McDonald that provide info on wiring basics!!Guitar Electronics
has some good info and wiring schematics, as well as parts for sale also!!
The Guitar Players Repair Guide is a great book I have had for years. I have saved a lot of money, learned a lot, and dont have to wait for some "dude" to get my axe fixed and then get overcharged for crapass work!! There are good techs out there, but in my travels, I have'nt run into many. If you play a lot of Live work, knowing the guitar is a lifesaver as well, because you dont want a bad switch or shorted circuit stopping your show at a bikers gig/roadhouse/night club in front of a bunch of drunken and mad folks!! Believe that!!
BTW, most shops will get 35 to 50 bucks to fix a short like you have in your guitar. (if the pickup isnt dead) That same money would set you up with all the tools and books you need to do it yourself....From now on!! Think about it. Good Luck....R Evans.>O