Help with "Brown Wire Mod"

Fellas, I could use some help with the brown wire mod I keep reading about, as I absolutely hate the thought of my AWD kicking on and off constantly.....the wear and tear on parts worries me a bit.

I read quite a bit on it and decided to go about it a bit differently.

It seemed to be that the best option was to run 2 wires out of fuse 104 under the hood (4x4 and clutch motor) to a relay. I wired the relay according to the diagram and then to a switch, all properly grounded.

Here's my problem, as per diagram I get no juice to the switch (check with voltmeter) I found the powered pole of the relay and switched one of my switch wires to that and I now have power to the switch, but it seems to be jumping through the relay, because I now can not control the 4x4 with my new on/off switch.

Could any of you guys provide me with a generic relay diagram or offer any ideas?

If I would have realized how ackward this relay would be I would've just bought a 30amp on/off switch and be done with it, which is what I have resulted to for now as our michigan roads seem to be getting snow here and there.

Any ideas? Thoughts?

Sorry for the horrible explanation, hope you guys can follow what I mean.

Nevermind.....I had created a constant loop outside of the relay.

Nice to have full control of the transfer case (as ford should have designed it)

I've attached a simple paint diagram for what I ended up doing. Hope this helps anybody out who may be interested in doing this mod.

Hmmm, I'd be interested in doing this and I think a lot of others would too... Maybe you should do a write-up if you have time?

Its cool that my 98 Navigator has a switch with 2H, A4WD, 4H and 4L.

so did you just pull the fuse, run a wire from each side with your own inline 30amp...then the relay...or tap the wire before the box..if pulling the fuse and putting a switch inline is an option id rather do that, just cause its easier than hunting the wire behind the dash..also..since you've done it have u noticed a difference..my front end seems to engage in reverse with wheel at full turn...love to get rid of that

Yes, I pulled the fuse (#104), inline fuse, relay, inline switch.

I would always feel the AWD engage when turning sharp from a stop sign, and in reverse as well. It became much more apparent when I installed the 285s.


For a short and simple write up-

I found a $12.00 30amp relay wiring kit from tractor supply company pre-made for fog lights.

After searching through the owners manual I found that fuse #104 controlled the transfer case motor and clutch.

Using the supplied wires with the inline 30amp fuses I plugged them into the notches in the junction block. I ran these wires through the drivers side fender well, and after notching the weather stripping near the kick panel ran them into the cabin under dash.

From there the relay was wired according to the diagram (with a little help from my voltmeter too) and then up to the switch where I notched the trim panel directly behind the steering wheel (it pops out really easy)

With the switch in the "on" position the loop now has continuous power and you have AWD, with it in the off position the GEM cannot read the ABS rings sensing slippage and now you have no power to the transfer case motor so you can leave 2 nice black marks on the pavement if you like.

Attached are some pictures for you guys. Sorry I didn't show my complete work, I have everything together and was just too lazy to take it apart. They show the jist of what I explained above.

Thanks for the pics and info.

Question... for the models with the 2wd, awd, 4 h, 4l... if they're in 2wd, is there any chance of AWD kicking in? I would assume not?

I have the 2wd

But after reading, when in reverse and turned full lock the front end makes like a poping sound like the tire is hopin. Kind of like if its in 4wd. But i only noticed it in reverse. Never in Drive though.

I'm going to give this a shot myself. I pulled the fuse to test the "2wd" mode and it worked great but of course I can't select 4HI/LO when needed.

It would actually be easier to tap the wire in the cabin if you can find it rather than have to to run 2 new lines cleanly through the firewall. I've not decided which way to go yet but it doesn't help that I can't find this wire at the described location in my passenger kick panel 12 pin harness. Other threads mention it runs on the driver side, one indicating you have to remove the seat and pull back the carpet to get to it.

If anyone knows specifically where in the cabin to look/tap on a 99 expedition let me know. If not I will probably start looking into working 2 wires through the firewall.

What some of you may be experiencing in reverse is the rear diff locking if you have the limited slip diff. One way to tell is get in some gravel or dirt (semi loose stuff) and cut the wheel hard and back up a few feet. If the inner tire mark has the gravel or dirt bunched up it was probably the diff locking.

One question for the OP. If you have the switch set to off you are basically killing power to the transfer case shift motor right? Meaning you would have to turn it back on if manually shifting into 4x4 hi or low. I like the idea of having a 2wd option instead of awd.