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Here is something I recently did to my other FJ, but could be applicable to most any Warn winch on an FJC or any other truck. For that matter, it could be done to almost any brand of winch, but I only have experience doing this on Warn winches so that is the focus of this post.
Warn makes some solid equipment, but some of their designs and specs are still using 1940's technology. Specifically, the electro-mechanical solenoids used to control the high-amperage power to the winch motor. There are usually four, two for powering the winch motor and drum "in" and two for "out". As an example, here are the solenoids from the Warn 8274 winch that I recently converted. The solenoids on a modern Warn planetary winch are either under a black plastic cover or integrated in the winch body/cover.
These solenoids are just old Ford tractor starter solenoids. They are prone to corrosion and failure, and can in fact fail in the closed position, which means your winch runs-on and can't be stopped without disconnecting the battery - not fun if you are winching "in"! Mostly though, they just quit working at the most inopportune time, right when you really need your winch.
A much better device for controlling winch motor power is the DC contactor. Contactors are much better sealed to corrosion, take up less space, and most importantly are designed to fail in the open position so your winch can't run-on. Some winch manufacturers (notably Superwinch) are making winches with contactors installed instead of solenoids from the factory. Even Warn is beginning to see the light; they now provide a contactor in their high-end Endurance 12.0 winch. Doubtless in the future they will move their other winches to contactor operation, but in the mean time, it's possible to upgrade your existing Warn winch in many cases.
There are a lot of different contactors out there for various applications; you need to choose one with an amperage rating and duty cycle suitable for your winch. The easiest way is just to use one that is made for a big truck winch (do not use one made for smaller ATV winches). Fortunately, Superwinch has made this easy for us - the Superwinch 90-14452 is suitable for most any winch likely to be used on an FJC or similar-weight truck. The cheapest place I have found to buy them is on-line from Summit Racing:
Superwinch 90-14452 - Superwinch Replacement Solenoids - Overview - SummitRacing.com
This single contactor will replace all four solenoids. Disconnect the negative terminal on the battery and remove all the solenoids and associated wiring. You will need to find a place to mount the contactor. With a little trial-and-error, I was able to fit mine inside the stock controller (solenoid) box on my Warn 8274 winch:
If it won't fit in your winch control box, you can mount it outside of the box or even inside the engine bay. I have seen them just bolted on to the end of the winch motor. One big advantage of mounting it inside the controller/solenoid space is that you will probably be able to re-use some or all of the stock power cables.
Wiring in the new contactor is actually much more simple than the rats nest of wires required for the four stock solenoids, and the Warn six-pin / five-wire controller used on almost all of their modern winches works perfectly. Use the attached PDF generic diagram to attach the power cables from the contactor to the winch motor and battery. If you can't re-use the short cables from the old solenoids to the winch motor, then go to a NAPA auto parts or similar store where they can make battery cables to any specified length. Have them made with 2-gauge AWG battery cable. Some Warn winches only use 4-gauge cables, but 2-gauge handles more amperage and provides a margin of safety. If you mount the contactor away from the winch, use plastic conduit to protect the cables from chafing and wearing through the insulation. These cables carry large current straight from the battery; you do not want them to short out!
Wiring in the stock Warn winch controller is simple. There are five wires coming out of the standard modern Warn controller. Connect the red wire to 12V+, it probably already has a 5/16" lug on it from being originally connected to a stud on one of the solenoids. Connect it to the same lug on the Superwinch contactor as the positive battery cable is connected to. Connect the black controller wire to a good ground. Again, it should already have a lug on it and be long enough to connect to the winch motor ground cable that goes straight to the battery negative terminal. The brown controller wire is a switched ground, and goes to the center spade terminal (marked black) on the Superwinch contactor. On my winch, the green controller wire is the "in" wire and gets connected to the right (marked blue) spade terminal, and the remaining white controller wire is "out" and goes the remaining left spade terminal (marked yellow) on the contactor. In my experience, some Warn winches have opposite "in" and "out" wiring, so check the operation with your controller and if "in" and "out" are reversed, just switch the green and white controller wires on the left and right (yellow and blue marked) spade terminals on the Superwinch contactor. Here is a photo of the completely-wired contactor and controller on my winch:
If you want to add an in-cabin winch control switch, just make double connections on the red, green, and white controller wires and run the extra wires into the engine bay and through the firewall into the cab.
My finished project is visually indistinguishable from stock, but is much more reliable and weather/waterproof:
The next time I have the Demello front bumper off of my FJC for any reason, I'm going to convert the Warn M8000 in it also.