[Michael C Henry]

I used a trick I came up with I used a 12V test light in place of the fuse. It acts like a capaciter in your power supply, not letting anymore current through than the test lights bulbs filament would let through.. With this limited power off, disconnect all the wires from the light switch except for the power supply Turn on the electric power (I'd just dissconnect and reconnect the test light). With all the load wires removed from the switch the test light should be off, if its on either the switch has an internal short or there is a short between the power supply and the switch. basically power is going to ground without doing any work(resistance)With everything connected and workingcorrectly the test light would be really bright but the actuall car lights would be dimm as the 12V test light wouldn't let enough current through to operate as usual. happy testing.