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Upgrading Factory 4 Pin to 4/7 Pin

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Old 06-29-2014, 09:28 PM   #1
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Default Upgrading Factory 4 Pin to 4/7 Pin

I recently picked up a '98 XLT with factory 4 pin towing. I want to upgrade it to 4 and 7 pin plugs. I saw the package you can get from etrailer but didn't want to spend that money if I didn't have to. So I made a trip to my local junk yard and as luck would have it I found a 2000 F150 with a factory 4 and 7 Pin harness (part number yl34-13a576-c321a) and a 7 pin plug. Anyone see any reason why this won't work? I plan on mating it with the combo bracket (YC3Z-14A163-CA). All at a total cost of under $10.

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Old 06-30-2014, 08:47 PM   #2
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It should work fine if you understand automotive wiring. Your 4 wires are for
1] & 2] left/right turn signal lights, and when both left and right are hot at the same time, that's your stop lights.
3] tail/running lights, and
4] ground.

The three wires you will add are for
5] trailer brake control,
6] hot 12-volt wire to charge the RV battery, and
7] backup lights on the trailer. Some folks use that backup light wire for something else, and most folks don't even connect it to anything (very few trailers have backup lights.)

The trailer brake wire is somewhat complicated to hook up. Do a search on etrailer.com and maybe you can find instructions. The simplest way is to tap into a brake light. If the brake light is on, then the driver wants the trailer brakes to work too. And you must use diodes and resisters and a fuse and all that electronic stuff I know nothing about. So do more research. But knowing what the 7 wires are for should get you started.
Grumpy ole man with over 50 years towing experience. 2012 F-150 Lariat SuperCrew EcoBoost, 6.5' bed, Platinum White/tan, Leer 100XQ camper shell, Nomad Joey 196S TT, CarMate 7x14' enclosed cargo trailer, three other utility trailers, plus a retired 2000 Keystone Sprinter 25RKS 5er we rarely tow now. ProPride hitch on the TT. Reese Strait-Line hitch on the cargo trailer.

Last edited by smokeywren; 06-30-2014 at 08:52 PM.
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Old 06-30-2014, 10:04 PM   #3
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Thanks smoke. I think I'm ok with the brakes. The harness has 4 plugs. One that goes back to the line that runs to the front of the truck. One for the 4 wire. One for the 7 wire and 1 for the rear brakes. I guess all I need now is the 4 and 7 pin combo bracket (on order from amazon) and maybe a relay or fuse.
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Old 07-01-2014, 09:12 AM   #4
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My 2001 came with a 4 pin. I bought the 7 pin, bolted it on, and plugged it right in. All of the wiring was already there. Easy breezy.

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Old 07-19-2014, 09:37 PM   #5
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Finally got around to putting the harness on. Worked like a charm.
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