Auxiliary switch for reverse lights.

[Haywire6000]

I have a flood light wired into my reverse lights, I recently wired a auxiliary switch into the reverse lights so I can use them as exterior work lights. I am going to wire it so the ignition had to be in accessory or on for the lights to work. That's not an issue. Just for a quick test, after I ran the wiring to the back of the truck( and connected it to the lights) I just hot wired it to the battery, I noticed that the battery light came on. The battery light only comes on when the ignition is off and I am running the reverse lights. Any idea why? I image I am back feeding something my jumping out the transmission switch with the engine off. Like I said though I plan on wiring it so the ignition has to be on or in accessory for the lights to work any way. Just wondering if anybody know why the batt light would be on.

 

[doorgunner]

Don't use the reverse lite wiring--it's causing too many problems....run the spotlite to a lighted toggle switch-then run a wire to the fusebox to an accessory fuse/key-on side of the fuse such as radio etc----but you'll have to put in a higher amp fuse.

 

[Haywire6000]

I ran a new wire to the back, where I tied into the lights. I like the fact that the light comes on when I go into reverse. Not that I am doubting you, but what kind of problems?

 

[Haywire6000]

Found why The batt light cam on, it's because I still had the truck in reverse (5 speed) and it was back feeding.

 

[LilDirty91Xlt]

I've done essentially the same, except my reverse lights supply power to a relay. Or my aux switch powers the relay. That way I don't need keys in the ignition to power my work lamps, and they just come on when in reverse.

 

[4.0B2]

this is my wiring plan for reverse lights that'll also work for work lights. I prefer to relay everything...

 

[Haywire6000]

The way I have it seems to work fine, the light it just a little dim running of the reverse switch, for my aux switch I have that wired to a relay. I think I'm going change it and use the revers switch at a signal for the relay, as well as the aux switch I wired. Next thing. Does anyone know if the reverse light on the switch side runs through the cab, or does it go straight from the tranny to the lights?

 

[Chris_North]

I'm not sure, TBH I think just hooking right into the tail light assembly is less of a headache. My relay is in the tail light itself, so far no problems. I don't make a lot of high water crossings tough...

this is my wiring plan for reverse lights that'll also work for work lights. I prefer to relay everything...

That's pretty much the same setup I have, except rather than run the toggle switch to the relay I used a SPDT switch with one option to provide power to the relay and the other just directly to the light. I could see yours being necessary for really big lights so that only one run of larger gauge wire is needed, but for anything under 90 watts IMHO it's not necessary and eliminates the need for the two diodes (you'd really only need one on the reverse light signal, the other is somewhat redundant). I'd also just tie the supply wire for the toggle switch into the primary for the light rather than having the separate fuse, but like I said I see the need if you run big lights. I have only a single 35w lamp right now and that's just a little shy of bright enough for me.

 

[4.0B2]

That's why the "?" Is on the other diode... Lol

Plus I like to overwire stuff. It'd probably be LEDs when it comes down to it so I should be good with a simpler wiring, I just want to over kill it and never have issues

 

[RonD]

In 12v systems relays are often easier to operate when you use the Ground as the control for the relay, instead of the 12v.

The Ford PCM(and most vehicle computers) operate on this principle, it grounds the injectors to open them, it grounds the coils to charge them.
Most factory relays are this way as well, reason being is that the 12v needed is usually only at certain locations in the vehicle, i.e. fuse panels and power boxes.

Since you only need to activate the relay why run extra wires, the ground is everywhere.

This means just one wire to a switch(or the PCM) is needed because it can be grounded locally.

 

[Chris_North]

You're absolutely right, I've honestly never considered that as an option. The only issue would be finding a place to pick up the reverse light signal ground, if it is in fact a switched ground someplace. I would think it would be, possibly on the shift linkage somewhere, but I never looked.

That's why the "?" Is on the other diode... Lol

Plus I like to overwire stuff. It'd probably be LEDs when it comes down to it so I should be good with a simpler wiring, I just want to over kill it and never have issues

Oh haha, you must have sneaked that in there when I wasn't looking. My outlook has always been to keep it as simple as possible so that when something does go wrong it will be easier to fix later. Different strokes for different folks I guess.

 

[4.0B2]

yeah it'd be just as easy to do it for the ground also...
on the rig we were wiring when that diagram was used, he has everything relayed and everything done on the positive side. that way works fine. It's used on a search and rescue jeep that has 2 Rigid Dually's on the rear.

Now that it's been said.. I think I might look into switching the ground side of it... that'd be stupid easy also.
Plus my thing with relays is this... I've had to many issues out of lights (even cheap autozone fog lights) when not relayed. So anything over a LED dome light (see my build thread's latest post).. I'll probably relay them all.


btw, I love threads like this.. just simple talking it out, he's this is my idea, then someone nicely saying You can improve that this way...
This is the way forums are suppose to work.

 

[RonD]

You're absolutely right, I've honestly never considered that as an option. The only issue would be finding a place to pick up the reverse light signal ground, if it is in fact a switched ground someplace. I would think it would be, possibly on the shift linkage somewhere, but I never looked.

You aren't using the reverse light ground.

You are adding a relay to the system, doesn't matter for what, the relay is controlled, Closed/Opened, by a ground and 12v passing thru it or not passing thru it.
You can of course ground the relay and send it 12v to close it.
Or you can also give it 12v and then ground it to close it.

So not related to what you are controlling just how the relay is being closed.
And a ground switch is usually easier, and safer, which is why they use them on hot wired devices like dome lights and horns, less chance of a 12v short.
A ground short just turns on the device, no smoke show, and that fragrant smell of melting plastic, lol.