Since you are going to most likely pull the switch to get at the 'master' wire to your dash lights you might as well take a look at the switch to see if it is indeed the problem. It might just be a loose wire. The guys here will jump at the chance to help you solve your problem. You just have to be their eyes and hands. A voltmeter or testlight are a big help and remember to disconnect your battery before poking around to much.

Six volt guy living in a twelve volt world