Keeps blowing the ignition fuse

Tiny
BKWOLF77
  • MEMBER
  • 2004 FORD F-150
  • 80,000 MILES
Blows the ignition fuse as soon as key is turned. Have replaced the ignition switch and have traced wires for breaks
Saturday, September 3rd, 2011 AT 4:27 PM

4 Replies

Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
What is fuse amp rating? Where is it located?
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Saturday, September 3rd, 2011 AT 4:53 PM
Tiny
CARADIODOC
  • MECHANIC
  • 33,873 POSTS
Breaks cause no current to flow. Fuses blow for excessive current, as in a wire rubbed through the insulation and grounding out to something metal. Components can also be shorted internally. That's rarely caused by the ignition switch.

A simple trick is to replace the blown fuse with a pair of spade terminals, then use a pair of small jumper wires to connect them to a 12 volt light bulb. When the short is present and the circuit is powered up, the bulb will be full brightness, so don't lay it on carpeting or against a plastic door panel. Now you can unplug things and move wire harnesses around to see what makes the short go away. When it does, the bulb will go out or get dim. The bulb's resistance will limit current flow to a safe value.
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Saturday, September 3rd, 2011 AT 4:56 PM
Tiny
BKWOLF77
  • MEMBER
  • 2 POSTS
Its a 20amp fuse located in the fuse box in the right kicker panel of the pasengers side
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Saturday, September 3rd, 2011 AT 4:59 PM
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
In the diagram below, The top wire is voltage to the ignition switch, comes from that fuse that keeps blowing, lite green wire with violet tracer. The bottom wires are feed from the ignition switch. Wires 1--6--7 are fuse protected.
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Saturday, September 3rd, 2011 AT 5:37 PM

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