Where to tap wiring for reversing light override switch

[casm]

2000 XJ, 4.0, AW4.

Searching has turned up plenty of threads on how to deal with flaky NSS issues leading to the reversing lights not working or how to wire in supplementary reversing lights, but I can't find any that cover what I'm looking to do. So:

If you've wired in an override switch to give you manual control over the reversing lights, where did you tap into the existing wiring? What I want is a switch that will give full manual control over reversing light operation - turn it on and they're always-on; turn it off and they work like they normally do. Power should be pulled from an always-on source so that it can be used without having to run the engine.

I did find this thread which has a circuit diagram for accomplishing this - but the author didn't mention where he tapped into the circuit. This is what I'm not clear on, and since there are a few options on this I'm looking for the cleanest possible route.

From digging through the FSM, my gut feeling is that it should happen at the brown/light green wire coming off of the NSS, but I'm not totally sure about this; I can usually follow circuit diagrams reasonably well but Chrysler's always seem to do my head in.

Any help most definitely appreciated in advance.

 

[s14unimog]

I would think the sensor on the transmission, but I'm not sure how you'll need to wire it in. Effectively you're just closing the loop on the circuit I would think. sorry not much help I guess

 

[kastein]

That wire goes from the NSS connector in the engine compartment (where you list it) all the way to the back of the Jeep, so somewhere along the way, it must pass by the front seats/doors. My bet is in the wiring harness running along the inside of the driver side rocker under the plastic trim... and I'm nearly certain that you can tap into it rather cleanly in the bulkhead connector behind the fusebox. You should also find always-hot 12V in there somewhere (brake light power would be a good choice, if the fuse is the same as the one for the reverse lights.)

EDIT: on a 2000 4.0 A/T XJ it goes through connectors C100, C200, and splice 142. It's fed by a 15A fuse (fuse 10 in the junction block.) Now that I think about it, the junction block on a late model is on the passenger side, and C100/200 are on the driver side nearish the OBD II port. Looks like C200 goes to the thicker wiring harness under the kick panel and rocker trim on the driver side. The fact that the connectors are on the driver side and the fuse panel is on the passenger side means you probably have a lot of choices on where to splice in if you feel like dropping the dash to get at the wiring harness (not sure it's accessible without dropping the dash, might be.) You're looking to power circuit L10 brown/light green to turn the light on.

 

[the_weirdo]

Here's how I did it on my 1998.

I used a relay. The trigger for the relay comes from two places: a switch that I wired to +12 volts and I also tapped into the wiring at the rear passenger tail light. When the shifter is put in reverse, the reverse wiring is powered and it sends power to the relay and the reverse lights are activated. Or when you hit the switch, power is sent to the relay and the reverse lights are activated.

You will need to use a diode, otherwise when you use the switch you will throw a CEL. I have a diagram of this wiring at home, will try to remember and post it tonight.

Edit: See post #9 here: http://www.jeepforum.com/forum/f20/hella-500ff-light-install-680124/
I did the same thing as this picture but I also used another input to pin 86 of the relay - the power wire from the reverse lights. It is the power wire from the reverse lights that needs to have a diode on it. If it senses voltage when the tranny is not in reverse you will get a CEL.

 

[kastein]

Good point. I had completely glossed over the fact that the TCU is wired into the reverse light circuit... :dunce:

 

[the_weirdo]

Good point. I had completely glossed over the fact that the TCU is wired into the reverse light circuit... :dunce:

Yeah, I found that out the hard way. Then did a search and found out about the diode.

Edit: Here is my wiring diagram. You can wire this up for the reverse lights or for aftermarket lights behind you. When you turn on your switch, the lights will go on. When your switch is turned off, putting the tranny in reverse will turn on the relay and turn on the lights.

 

[stewie]

i believe the wire that i tapped into for my aftermarket lights was in the door trim at the floor drivers side. i dont remember the color in my 95, but i traced it from the bulb forward. BTW i wired up a set of fogs on a relay controlled by a 3 position switch- aux lights manually on, aux off, aux on with stock back up lights.

 

[casm]

Edit: Here is my wiring diagram. You can wire this up for the reverse lights or for aftermarket lights behind you. When you turn on your switch, the lights will go on. When your switch is turned off, putting the tranny in reverse will turn on the relay and turn on the lights.

Thanks for that; it looks to be the simplest way of plumbing everything in. I'll go with this instead of screwing with the NSS.

i believe the wire that i tapped into for my aftermarket lights was in the door trim at the floor drivers side. i dont remember the color in my 95, but i traced it from the bulb forward.

Sounds reasonable, and I suspect mine is run similarly.

Thanks, folks - this will definitely make tearing into the wiring much easier.