Dandy. There's a wire to the radio hooked to the tail lights to tell the display when to dim and another wire hooked to the dash lights to tell the display how much to dim. Very often, with aftermarket radios, those wires get used as grounds or they're spliced with electrical tape that unravels on a hot summer day into a gooey mess and lets the wires short against the radio's case. That's why I asked if it was the original radio.
A simple trick to finding a short is to replace the blown fuse with a pair of spade terminals, then use small jumper wires to connect them to a 12 volt light bulb. A brake light bulb works well. When the circuit is live and the short is present, the bulb will be full brightness and hot so be sure it's not laying on the carpet or against a plastic door panel. Now you can unplug electrical connectors and move things around to see what makes the short go away. When it does, the bulb will get dim or go out.
If you do this to the tail light circuit, you can drive that way during the day when those lights aren't needed but since there's so many bulbs on the car, the test light is going to be fairly bright already. You will need to notice when the bulb gets a little brighter which is when the short occurs. I know this sounds complicated but you might also try this with a head light bulb in place of the blowing fuse. A brake light bulb will limit current flow to less than an amp which isn't enough to run all the tail light bulbs on the car. A head light bulb will pass about five amps and will give a better indication in this case when the short is present. With that bulb in the circuit, you can wiggle wiring harnesses, poke at connectors, and try different things to see what makes the short appear or go away.
Friday, April 27th, 2012 AT 8:33 PM