Need Help with Circuit for Tying Rear-Facing Amber Light into Factory Backup Lights and 4-way Flasher

[Mr. Bills]

I need help from the auto wiring experts:

This is what I am trying to accomplish with the simplest and most reliable wiring schematic possible (think “Jeep Wiring for Dummies”):

Circuit for a single rear facing amber light with 12v/55 watt H3 halogen bulb;

10 amp circuit capacity although the single light will draw less than 5 amps (3.74 amps @ 14.7 v);

Dash mounted “on-off-on switch” for rear-facing light:

On #1 - Light turns on with switch

On # 2 - Light turns on automatically with factory backup lights otherwise off

Off – Light stays off.

Now let’s complicate things:

I would also like the rear facing amber light to flash automatically when the 4-way flashers are turned on but with the “off” position of the on-off-on switch disabling this feature, i.e., the rear facing light will not flash with the 4-way flasher when the on-off-on switch set to the “off” position but would flash automatically when the 4-way flashers are turned on when the on-off-on switch is in either the “On #1” or “On #2” position.

Can this be done? If so, how? Can one tap into the factory backup light wiring to trigger the rear-facing light AND tap into the 4-way emergency light feature all in the same circuit? What will I need to tap and where? I am not good at reading vehicle wiring schematics and need someone to interpret the diagram for my ’06 Rubicon and tell me the wire color(s) I need to find. Also, what about short circuits and “back feeding” (whatever that is) in a circuit like this? (Am I going to have to learn about diodes to make this work?)

Please help.

As Harry Callahan famously said, “A man’s got to know his limitations.” One of mine is electrical wiring.

 

[RubiconMike]

Mmmm, I think I could make it work with two switches (and a relay).

If I understand correctly, you want the light to come on with one of three things:

1. manual switch
2. backup lights
3. emergency flashers.

but you also want to switch it off entirely. I think I would need a second switch to do that.

I think I could make it work with only one switch but it would always be connected to one of the three, so unless you wanted manual or flashers, you would leave it in the middle position so it would only come on with the backup lights.

Upon further thought, maybe a four-position rotary switch:
1. manual switch
2. backup lights
3. emergency flashers
4. nothing

 

[Mr. Bills]

If the square emergency flasher button still activates the vehicle lights plus the rear-facing amber then I think the option of manual, backup light, and emergency flasher would work because in normal circumstances having the on-off-on switch in the emergency flasher position would effectively still serve as an off position. (i.e, nothing would turn on in that position of the on-off-on switch until the square emergency flasher button is activated).

Tell me more.

 

[RubiconMike]

I think this should work for you. Make sure the DPDT (double pole, double throw) switch is an "on-on-on", not an "on-off-on" switch. Google it and you should be able to find one fairly easily. You will need to jumper terminals 3 and 5. The relay is a standard Bosch or similar relay that you can get at any auto parts store.

Basically, you are using a relay to channel power from the battery directly to the light. The relay is grounded and only needs a positive 12v to trigger it. That positive 12v is supplied by the switch. The input to the switch is positive 12v from the battery (or switched ignition if you want it to turn on and off with the key), the backup lights, and the emergency flasher. The illustration in the box below the wiring diagram shows the electrical connections for all three switch positions. I diagrammed it with the emergency flasher in the center position (your "off" position), but by connecting to different terminals you can make it any switch position you want. Let me know if you need more info.

 

[RubiconMike]

As for tapping into your vehicle wiring, you only need your three positives to the switch (if you want the manual on to be controlled by the key switch). If you want to manually turn the light on without the key, you only need to find 12v from the backup lights and flashers (the manually on comes directly from a battery source). You should be able to tap the backup lights at the fuse box, as well as switched ignition. You might be able to tap the emergency flashers there also, check the fuse box and see if there is one specifically for them. No diodes are needed because you will never be back feeding into any circuit.

If you don't have one yet, you should get a SnapOn or equivalent neon circuit tester: http://rover.ebay.com/rover/1/711-5...0001&campid=5337789113&icep_item=273599444555

You can probe wires and fuse box terminal to find which is hot.

 

[Mr. Bills]

Wow, thanks!

I'll have to stare at the schematic for awhile to be sure I understand it.

As far as the switch is concerned I've found a few mini DPDT on-on-on toggle switches on Amazon but they appear to be selector switches for electric guitars. I'll keep looking. It would be nice to find a rocker switch but so far everything has been a toggle.

I found a related thread on another jeep forum that mentions tapping into the wire harness under the drivers side door for the reverse light wire - identified as a violet wire with black stripe. I can confirm that with a test light or by looking at the wire color at the tail light itself.

Tapping into the emergency flasher circuit has me stumped. I'll need some help there.

One post on the subject mentioned that an indicator light would be helpful to know at a glance whether the rear-facing light is on. Can this be added to the circuit somehow?

 

[Mr. Bills]

Update:

I have found one "regular size" DPDT on-on-on toggle switch with spade connectors rather than soldered connections which would make wiring much simpler for me:

https://www.steinair.com/product/toggle-switch-3-position-dpdt/

I would like to use it in conjunction with this toggle switch guard:

https://www.steinair.com/product/toggle-switch-guard-yellow-plastic-spring-loaded/


This would necessitate the switch being wired so that "Manual On" is at the top, "Backup Lights" are in the center, and "Emergency Lights" are in the bottom position so that the toggle switch cover can be closed with the switch in the position that is effectively "off" unless the square emergency light button is used.

Another feature that would be very cool is an indicator light for when the switch is in "Manual On" and "Backup Lights." Since the rear facing light can't be seen from behind the wheel during daylight, this would alert to the light inadvertently being on while driving. It wouldn't really be necessary to operate for "Emergency Lights" but wouldn't hurt if it did.

https://www.steinair.com/product/amber-led-indicator-light-12v/

Can this work? If so, what has to be changed in your schematic to make it work that way?

 

[RubiconMike]

Nice find on the switch, looks perfect.

Here's an updated diagram, I used the drawing of the switch bottom from the manufacturer's website, so it should exactly match what you get.

Adding the dash light is easy-peasy. Just run the positive to the same wire that triggers the relay (#2 on the switch). Whenever the rear light is on, the dash light will be on also.

I placed items on the diagram to make it easy to indicate wiring connections. I would suggest putting the switch and LED in the cabin where convenient and the relay near the battery. The +12v going to #6 on the switch does not need to come from the battery. Since it will only be handling a small amount of current to trip the relay, you can pull it from any convenient source in the cabin. This is the power for the manual activation. If you are using switched power (on/off by the key), and you forget to turn the light off, it will automatically go off when you turn off the key - but you will have to have the key on to manually turn on the light. If you use unswitched power you can turn the light on without the key, but if you forget and leave it on, it could run down the battery (eventually). Pick whichever seems most useful to you.

An easy place to get power for stuff like this is at the back of the cigarette lighter. Mine has two - one is switched and one is not - how handy is that?

Your profile says you have a Rubicon Unlimited (good choice!) so it must be an '05 or '06. My factory manual is from my '03 and I think they may have changed the wiring colors. FWIW, it shows the backup light wire as violet with a white stripe. I could not find a wire to trigger the Hazard lights. Maybe someone on this forum can help with that.

 

[Mr. Bills]

I am impressed. And thankful.

The schematic makes sense to me, which is a feat. I shall now start gathering the parts.

The jumper is still between terminals 3 and 5, correct?

The one unanswered question at this juncture is where to tap the emergency flasher circuit to get the rear facing light to operate with the emergency lights.
Wire color and location would be a home run.

Anyone?

 

[RubiconMike]

Yes, just take a short piece of wire, crimp a female spade on each end, and connect terminals 3 and 5.

Sorry I don't have time to go poking around the wires on the steering column harness for the flasher wire. Given some time (or the correct factory manual) I'm sure I could find it. The flasher is under the plastic steering column cover, next to the switch.

 

[Mr. Bills]

I presume that all I need to find are the two wires that connect to the flasher and tap into one of those. If so, I have a 50/50 chance of finding the right one on the first try and a simple test light should be all I need to do that.

Again, thanks for your help.

 

[MountaineerTom]

Please help.

As Harry Callahan famously said, “A man’s got to know his limitations.” One of mine is electrical wiring.

I feel your pain. I have no confidence when it comes to wiring. The physical part of crimping/connecting/soldering/heat shrinking, I have not problems with. It's the part on using relays and connecting everything up correctly that I struggle with. I research and research and still have to ask questions to confirm to get the confidence. LOL

 

[Mr. Bills]

I am having trouble with the last bit of my wiring plan - finding where to tap into the 4-way flasher circuit in order to bring Rubicon Mike's schematic to life.

I have looked in the wiring chapter of the 2006 Jeep Wrangler Factory Service Manual, linked here: https://wranglertjforum.com/attachments/2006-tj-service-manual-pdf.14047/

In particular, I have looked at the pages shown below. Its Greek to me, especially after I found a subsequent subsection on splicing into circuits which is ancient Greek to me.

Can anyone who understands schematics suggest to me where I should tap into the circuit? Which color wire is shown?

I'll owe you big time.