Brake and blinker fuses keep blowing out

WEIRGOR

MEMBER
1992 FORD F-150
5.8L
V8
4WD
AUTOMATIC
130,000 MILES

Truck was fine. I hoped in it this morning and I had no brake lights or not turn signals. I replaced the fuses to both the brakes and the blinkers but they blew out as soon as I put them in. I crawled underneath the truck back by the rear bumper and could find no short anywhere. This was only a visual check. What could be my problem?

Thursday, January 29th, 2015 AT 10:41 AM

1 Reply

CARADIODOC

MECHANIC
34,094 POSTS

The trailer harness is still a good suspect, especially when multiple circuits are involved.

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.

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Thursday, January 29th, 2015 AT 10:45 AM