Trailer Plug Blues
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Postmaster
Joined: Aug 2005
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From: Lancaster, MA
Trailer Plug Blues
Finally got around to putting a new hitch and wiring on my '99 F350 today. The previous owner has some generic universal hitch on there, so I stepped it up to a 15K pound hitch. My problem is with the wiring. Bought the plug in for it because the truck has the trailer tow package. The previous owner had hacked the crap out of the plug in on the truck side, so I ended uo cutting off the ends and just hard wiring it. Everything works perfectly except for the hot wire. I have no power going to the plug. The fuse is good. The only thing I'm not sure of is the relay. The manual has it listed as relay #38 but I can't locate it anywhere and it doesn't show it on the schematic in the manual. The hot wire should be the orange one, correct? I'm getting no power from in front of where the hack job was (where it is still factory wiring) so I know that isn't the problem. Any help would be great.
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Joined: Aug 2005
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From: Lancaster, MA
I did test it with the key on and then the truck actually running. Then I checked things like the right turn to make sure my test light was grounded properly and working.
As far as the power distribution box, I think I checked it. Is that the box that's located under the hood? I could only find one box there (pretty much looks like a fuse box with large sized fuses and a few relay) and I checked that but could not locate the relay for the hot wire. Like I said, everything else on the trailer plug works as it should, both on the 7 round and the 4 flat. The only other thing I can think of is that the plug itself is a newer style one like what you would find on '08 and newer trucks. I like how the look and the corrode less. I'm sure that would have nothing to do with it, but I figured I's toss that info out there anyway.
As far as the power distribution box, I think I checked it. Is that the box that's located under the hood? I could only find one box there (pretty much looks like a fuse box with large sized fuses and a few relay) and I checked that but could not locate the relay for the hot wire. Like I said, everything else on the trailer plug works as it should, both on the 7 round and the 4 flat. The only other thing I can think of is that the plug itself is a newer style one like what you would find on '08 and newer trucks. I like how the look and the corrode less. I'm sure that would have nothing to do with it, but I figured I's toss that info out there anyway.
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Postmaster
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From: Lancaster, MA
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FTE Legend
Joined: Jul 2005
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From: Millersville, MD
Did you happen to look at a schematic wiring diagram of the '99? What did it show?
Wouldn't it be easier to just install a fused NEW line from the battery to the closest point to that wire that goes to the 7 way plug? My "extra relay" box it in FRONT of the driver's side battery..... but then, mine's an 05
Wouldn't it be easier to just install a fused NEW line from the battery to the closest point to that wire that goes to the 7 way plug? My "extra relay" box it in FRONT of the driver's side battery..... but then, mine's an 05
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Joined: Mar 2003
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From: Farms of Duplin County
My 2001 has a two smaller relay boxes that holds two relays next to the large relay/fuse box under the hood. The one closest to the firewall is the one you should check. I am willing to bet your missing a relay in there.
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Joined: Aug 2005
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From: Lancaster, MA
I'll check everything over again tomorrow when I get some time, hopefully. If I can't find anything, I may just have to run a hot wire from the battery, but I'd prefer not to.
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From: Lancaster, MA
OK, so I'll finally have some time to tackle this issue next week. I'm probably just going to end up running a hot wire from the battery back to the 7 round plug. Of course it'll have to be fused, but what size fuse should I use? 10 amp? Also, what color wire should I tap into at the 7 round? Is it the orange wire or ???
