Wiring issues for trailer plug-in
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3rd Gear
Joined: Oct 2022
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Wiring issues for trailer plug-in
I put a flatbed on my pickup and I am having a hard time with the wiring for the 7 way plug. It had on on the original ford bed, but it didn’t work when I bought it. There are two plugs coming off the back frame that the original plug was wired into before I took the bed off. These plugs don’t have any power. I can’t find any info on fuses or relays related to the factory wiring for trailer plug ins. I’m new to this ford pickup thing, any help would be greatly appreciated.
Logistics Pro
Joined: Nov 2013
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From: Mojave, Ca
All the fuses for the body lights are located in the fuse box near the driver's knee. All the fuses and relays for the trailer lights are in the power distribution panel under the hood. Pull each one and inspect all the fuses very carefully for being blown or corrosion.
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3rd Gear
Joined: Oct 2022
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All the fuses for the body lights are located in the fuse box near the driver's knee. All the fuses and relays for the trailer lights are in the power distribution panel under the hood. Pull each one and inspect all the fuses very carefully for being blown or corrosion.
Thanks a bunch.
Tuned
Joined: Dec 2013
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From: Corinth, TX
Last edited by Scott in TX; Nov 3, 2022 at 01:55 PM. Reason: wrong info
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3rd Gear
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I have a 1990 N/A f350 single wheel.
I think it’s setup a little differently. Getting the feeling it did not come from the factory with any stock wiring for a trailer hookup.
I think it’s setup a little differently. Getting the feeling it did not come from the factory with any stock wiring for a trailer hookup.
Last edited by BCK199073; Nov 3, 2022 at 03:40 PM. Reason: Adding
Logistics Pro
Joined: Sep 2007
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From: Western Mass
1990 was setup differently, no fusebox under the hood, just a bundle of fusible links coming off the starter relay.
There was some factory wiring for trailers, my '88 F250 had some original wiring and connectors heading to the back for trailers, but someone had spliced in a 7 way into the bed for a 5th wheel. I think I identified the two connectors you're talking about in the rear, but didn't have the other end to plug into them, and it seemed like an obscure ford only part that I wasn't going to waste time trying to find. There is bundle or two that runs from the firewall to the back of the truck. One of them I remember being only 4 wires and looked like it was supposed to do something with the trailer wires, but they didn't all connect at the front? I ended up cutting at least some of them off to run a 12V line and the trailer brake line to the rear. Then I ended up making my own relay box that I mounted in the bed and connected to the wiring going the the rear lights.
There was some factory wiring for trailers, my '88 F250 had some original wiring and connectors heading to the back for trailers, but someone had spliced in a 7 way into the bed for a 5th wheel. I think I identified the two connectors you're talking about in the rear, but didn't have the other end to plug into them, and it seemed like an obscure ford only part that I wasn't going to waste time trying to find. There is bundle or two that runs from the firewall to the back of the truck. One of them I remember being only 4 wires and looked like it was supposed to do something with the trailer wires, but they didn't all connect at the front? I ended up cutting at least some of them off to run a 12V line and the trailer brake line to the rear. Then I ended up making my own relay box that I mounted in the bed and connected to the wiring going the the rear lights.
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Mountain Pass
Joined: Nov 2011
Posts: 100
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From: Wilton, IA
My guess is those are not factory plugs. Not very common back then like it is today.
So that means someone wired that in. And usually, they did a splice up under the box around the frame.
But typically, those connections were not very well done to last years of moisture, dirt, grime etc.... Likely that connection is now corroded or maybe even completely disconnected. You will likely see butt connectors in the factory taillight wiring or an area that is wrapped with electrical tape. That electrical tape likes to trap moisture and grime in their over time.
I'd start tracing the wire from the 7-way plug and see what you find.
Good luck. Trailer wiring is fun.
So that means someone wired that in. And usually, they did a splice up under the box around the frame.
But typically, those connections were not very well done to last years of moisture, dirt, grime etc.... Likely that connection is now corroded or maybe even completely disconnected. You will likely see butt connectors in the factory taillight wiring or an area that is wrapped with electrical tape. That electrical tape likes to trap moisture and grime in their over time.
I'd start tracing the wire from the 7-way plug and see what you find.
Good luck. Trailer wiring is fun.
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