Have a person at each nav light. Turn the nav light switch on to determine if they all come on, but don't wait for the switch to trip. That could be overheating the wiring and causing unseen damage. Most likely you'll have one that doesn't, or is extremely dim.
I would then remove the nav light wire(s) from the load side of the switch. Engage the switch and see if the switch trips. If it does, then the switch should be the culprit. If it doesn't, then it's a matter of finding the shorted wire. If your lucky, you still have three wires that were attached to the switch. They should be labeled L17A18 (Tail), L18A18 (Right) and L19A18 (Left). Remove the nav light bulbs and check each wire for a short to ground.
Tracy Ryan2010-07-12 23:02:32