Fuse blows

SIMSJAMES4325

MEMBER
1991 DODGE DYNASTY
3.3L
6 CYL
2WD
AUTOMATIC
192,568 MILES

The number twelve fuse blows almost immediately. This fuse is in the glove box it controls the vanity lights and radio. It started doing this when we had a new radio installed. I have checked and checked the wiring on the new radio it is right. So can someone help?

1 Reply

CARADIODOC

MECHANIC
33,916 POSTS

Chances are it is the new radio. A potential clue is the fuse will not blow when the dash lights are turned to their dimmest level. If that happens, someone tried to find a ground wire in the radio's two two original plugs and mistakenly found what is not really a ground wire. The best test is to just unplug the new 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 twelve 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 is 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.

In this case, see if the test bulb dims or gets brighter when you turn on the running lights or adjust the dash lights.