Fog light issues
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5th Gear
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Fog light issues
I am trying to track a sporadic shorting wire in the Fog Light circuit..upstream, fuse 27, 5amp. New switch and relay, still will blow the fuse....sometimes right away, maybe a hour of driving. If I barely touch that huge ball of wires under the hood going into the Power Distribution Box it blows instantly. So.....that's the issue. My Chiltons show white/black (hot) and yellow (ground) from switch in cab to the relay in the PDB. If someone could confirm that for a 2003 F-150 FX4 since my Chiltons only goes to 2002. I use to be a very active member here but I had to open a new account to get back in. Thanks for any help....Spotty.
Hotshot
Joined: Jan 2004
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From: St Louis
WT/BK from F27 to fog light switch, YE to fog lights.
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5th Gear
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I ended up cutting the friction tape that held the ball of wires together at the PDB. I sprayed down all the wires with contact cleaner and also noticed rust marks on the wires that rubbed on that metal plate. No wires seemed rubbed thru. I cut a thin piece of plastic to put between the wire bundle and that somewhat rusty plate. Seems to be working now but still can't figure out what wires come from the fog light switch to the PDB relay. Is it yellow and white/black?
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5th Gear
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OK...Thank you. So the power for the Fog Light Switch comes in on W/B from the 5amp. fuse in #27 and exits the switch once turned on , to the coil on relay 205 in the PDB as solid yellow?
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Hotshot
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From: Near Salt Lake City
I think he is asking where the power comes into his PDB from? On the yellow wire?
He needs a power and ground distribution diagram it sounds like
Just know those fog lamps circuits melt connectors and everything else they touch
Headlight switches on the old T Birds and Mustangs melted daily
Check the connectors for being melted and the wiring for being hard as a rock
He needs a power and ground distribution diagram it sounds like
Just know those fog lamps circuits melt connectors and everything else they touch
Headlight switches on the old T Birds and Mustangs melted daily
Check the connectors for being melted and the wiring for being hard as a rock
Last edited by manicmechanic007; Jan 4, 2026 at 10:26 AM.
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5th Gear
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Thanks Don, that is perfect. It confirms the yellow comes from the switch to the relay coil (hot). My issue is all upstream not downstream. I moved that wire bundle away from that metal plate and my problem (blows #27) seems to have gone away. Now I can recheck that area focusing on the yellow.
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