Reversing light +12v?

FieldMonster · Nov 23, 2023

My dashcam, like a lot of modern dash cams, has a rear view camera with a handy dangling red wire that can optionally be connected to the positive 12 volts of the reverse light. This allows the display to switch to the reverse mode, complete with guide lines. (I know the car has this anyway, but the display on my dashcam is better!)

As a quick hack I’ve wired it to the drivers side interior footwell wiring, so I can manually switch it to reverse mode with a flick of an overhead switch. While fun, it would be neater to have it engage when the car goes into reverse gear without any additional intervention.

Has anyone tapped into their reverse light circuit, either via a fuse (I can’t see any relevant fuse anywhere?) or the wiring near the rear lights, or via the light cluster itself? I think the little hatch in the back on the drivers side (opposite the bottle jack hatch) is probably the right territory, but I’d appreciate any tips.

Clark Kent · Nov 23, 2023

FieldMonster said:
My dashcam, like a lot of modern dash cams, has a rear view camera with a handy dangling red wire that can optionally be connected to the positive 12 volts of the reverse light. This allows the display to switch to the reverse mode, complete with guide lines. (I know the car has this anyway, but the display on my dashcam is better!)

As a quick hack I’ve wired it to the drivers side interior footwell wiring, so I can manually switch it to reverse mode with a flick of an overhead switch. While fun, it would be neater to have it engage when the car goes into reverse gear without any additional intervention.

Has anyone tapped into their reverse light circuit, either via a fuse (I can’t see any relevant fuse anywhere?) or the wiring near the rear lights, or via the light cluster itself? I think the little hatch in the back on the driver side (opposite the bottle jack hatch) is probably the right territory, but I’d appreciate any tips.

Hi FM.
Here's a suggestion if you have the towing option.

Temporarily join the DRW (dangling red wire!) to pin 8 of the trailer socket. Pin 8 is the reverse signal and is at the 12 o'clock position, closest to the cover hinge. Use a long jumper wire. Test for 12V at pin 8 while in reverse to ensure you have the correct pin before attaching the DRW.
Start your vehicle, select reverse and check you get the result you expect on the camera without producing a trailer lights error.
If all is good, remove the jumper wire.
Remove the right side rear trim and locate the trailer harness connector. It's the rectangular connector at the top in this pic. Identify and confirm the reverse wire with a multimeter. On my vehicle it's a blue wire with an orange trace. Join the DRW to the reverse wire adjacent to the harness connector using a tap method of your choice: posi-tap, solder splice, etc. I would put a 1 or 2 amp fuse inline with the DRW just to be safe. Test again. When you're happy, tidy up and celebrate

FieldMonster · Nov 23, 2023

Amazing! Thank you super.. I mean Clark

I do have the towing option so hopefully my setup will be similar. My multimeter will be coming out this weekend!

If I may ask one follow up, I’ve not removed the right rear trim before. Any tips on the best place to start? Keen to not create any rattles.

Korg · Nov 23, 2023

Clark Kent said:
Hi FM.
Here's a suggestion if you have the towing option.

Temporarily join the DRW (dangling red wire!) to pin 8 of the trailer socket. Pin 8 is the reverse signal and is at the 12 o'clock position, closest to the cover hinge. Use a long jumper wire. Test for 12V at pin 8 while in reverse to ensure you have the correct pin before attaching the DRW.
Start your vehicle, select reverse and check you get the result you expect on the camera without producing a trailer lights error.
If all is good, remove the jumper wire.
Remove the right side rear trim and locate the trailer harness connector. It's the rectangular connector at the top in this pic. Identify and confirm the reverse wire with a multimeter. On my vehicle it's a blue wire with an orange trace. Join the DRW to the reverse wire adjacent to the harness connector using a tap method of your choice: posi-tap, solder splice, etc. I would put a 1 or 2 amp fuse inline with the DRW just to be safe. Test again. When you're happy, tidy up and celebrate

...and be careful not to get run over by a reversing Ineos in the process!

Clark Kent · Nov 24, 2023

Korg said:
...and be careful not to get run over by a reversing Ineos in the process!

Yep, that too! Kinda goes without sayi.. Never mind

Clark Kent · Nov 24, 2023

FieldMonster said:
Amazing! Thank you super.. I mean Clark

I do have the towing option so hopefully my setup will be similar. My multimeter will be coming out this weekend!

If I may ask one follow up, I’ve not removed the right rear trim before. Any tips on the best place to start? Keen to not create any rattles.

You would think I could exactly recall how I did that but nope, not really

. Search the media gallery. Others have posted about it.

I don't remember it being especially hard but it's a big piece of plastic trim so treat it nice.
Lift the floor out. Remove the tie down rings. Remove the black plugs and the nuts underneath (12mm deep socket?). I think I removed the trim across the floor behind the seat back but on reflection maybe I didn't need to do that.
Unclip the panel from the edges. Pic shows the clip locations (holes). I think the top edge came off last and went on first. The front bottom corner was a PITA so go easy there. It might be easier to remove or loosen the lower C pillar cover next to the seat. I didn't, but that was the hardest part because of how the trim sections nest together.

A good set of trim tools are your friend for this job. Not essential if you hate your fingers, just go at it. The clips in the middle section are unexpected. They will pop out if you pull on them straight, don't peel them apart or they will likely break off. Look at the pic for the line of trim-plug sized dimpled holes between the window and the inner guard.
Reinstalling is the reverse. Go easy. Start after 7pm. Wear something nice

Bring flowers.

FieldMonster · Nov 24, 2023

That’s super helpful. Really appreciate it. I’m very much looking forward to Saturday morning now.

Grey Wolf · Feb 2, 2024

Clark Kent said:
Hi FM.
Here's a suggestion if you have the towing option.

Temporarily join the DRW (dangling red wire!) to pin 8 of the trailer socket. Pin 8 is the reverse signal and is at the 12 o'clock position, closest to the cover hinge. Use a long jumper wire. Test for 12V at pin 8 while in reverse to ensure you have the correct pin before attaching the DRW.
Start your vehicle, select reverse and check you get the result you expect on the camera without producing a trailer lights error.
If all is good, remove the jumper wire.
Remove the right side rear trim and locate the trailer harness connector. It's the rectangular connector at the top in this pic. Identify and confirm the reverse wire with a multimeter. On my vehicle it's a blue wire with an orange trace. Join the DRW to the reverse wire adjacent to the harness connector using a tap method of your choice: posi-tap, solder splice, etc. I would put a 1 or 2 amp fuse inline with the DRW just to be safe. Test again. When you're happy, tidy up and celebrate

Hi , I have installed my wolfbox with the DRW splices in to what I believe is the reverse light for the trailer. I picked it up from inside the car next to the connector block on the rear right hand side. The only issue I have is that I get a trailer light error now. Do you have any ideas as to how I can correct this? My vehicle has just the 13 pin trailer connection. Thanks

Clark Kent · Feb 3, 2024

Grey Wolf said:
Hi , I have installed my wolfbox with the DRW splices in to what I believe is the reverse light for the trailer. I picked it up from inside the car next to the connector block on the rear right hand side. The only issue I have is that I get a trailer light error now. Do you have any ideas as to how I can correct this? My vehicle has just the 13 pin trailer connection. Thanks

Presumably you only get the trailer light error while you're in reverse?
It's a problem many have had with trailers behind the Grenadier when their trailer uses led lights. The current flow is lower than the vehicle expects to see so assumes a lamp has failed and sets the warning light ON. In your case the minimal load of the camera trigger circuit is confusing the vehicle. You could add a resistor in line with the camera wire to increase the load, or just ignore it. There are resistors available to solve this for led lamps but I can't say how this would work with the camera.

Grey Wolf · Feb 4, 2024

Clark Kent said:
Presumably you only get the trailer light error while you're in reverse?
It's a problem many have had with trailers behind the Grenadier when their trailer uses led lights. The current flow is lower than the vehicle expects to see so assumes a lamp has failed and sets the warning light ON. In your case the minimal load of the camera trigger circuit is confusing the vehicle. You could add a resistor in line with the camera wire to increase the load, or just ignore it. There are resistors available to solve this for led lamps but I can't say how this would work with the camera.

Yes, only when selecting reverse, the camera image displays the reversing lines and the car then displays a trailer light fault, but not every time.

Clark Kent · Feb 4, 2024

Grey Wolf said:
Yes, only when selecting reverse, the camera image displays the reversing lines and the car then displays a trailer light fault, but not every time.

Ok. Here's a better explanation. Note the recommendation is to install a resistor across the load, not inline. That makes sense. So in your case you would install a resistor between the red trigger wire and the earth cable of your camera. If you want to pursue a solution look for something like this locally. 6 Ohms seems to be the go.

Grey Wolf · Feb 4, 2024

Clark Kent said:
Ok. Here's a better explanation. Note the recommendation is to install a resistor across the load, not inline. That makes sense. So in your case you would install a resistor between the red trigger wire and the earth cable of your camera. If you want to pursue a solution look for something like this locally. 6 Ohms seems to be the go.

View attachment 7842465

Thank you that's very helpful . Can I put it between the red trigger wire and earth it to the car body? I have attached some pictures so you can see what I have done . Thanks

Clark Kent · Feb 4, 2024

Grey Wolf said:
Thank you that's very helpful . Can I put it between the red trigger wire and earth it to the car body? I have attached some pictures so you can see what I have done . Thanks

It's worth a shot. Peel back the tape where you tapped into the reverse circuit then temporarily add a resistor between the red wire and one of the earth studs. See if the light still comes on in reverse. It's not a perfect solution but might be enough to do a quick test.
From memory, but please check, the white wire is the earth return for the trailer circuits. If you can, install the resistor between the red camera wire and the white wire so the resistor load is applied across the reverse circuit only. You could push a test probe into the back of the connector to pick up the white contact. Then join the resistor to the probe. If that works you have your solution.

jert · Jul 10, 2024

Clark Kent said:
It's worth a shot. Peel back the tape where you tapped into the reverse circuit then temporarily add a resistor between the red wire and one of the earth studs. See if the light still comes on in reverse. It's not a perfect solution but might be enough to do a quick test.
From memory, but please check, the white wire is the earth return for the trailer circuits. If you can, install the resistor between the red camera wire and the white wire so the resistor load is applied across the reverse circuit only. You could push a test probe into the back of the connector to pick up the white contact. Then join the resistor to the probe. If that works you have your solution.

did your final install work @Grey Wolf ? Any pictures to share ?

Grey Wolf · Jul 10, 2024

jert said:
did your final install work @Grey Wolf ? Any pictures to share ?

I didn't have to add a resistor in the end.. I just spliced the red wire into the reverse lights as per the photo attached and it has been good for 6 months now with no issues.

flynnsk · Jul 18, 2024

Clark Kent said:
Hi FM.
Here's a suggestion if you have the towing option.

Temporarily join the DRW (dangling red wire!) to pin 8 of the trailer socket. Pin 8 is the reverse signal and is at the 12 o'clock position, closest to the cover hinge. Use a long jumper wire. Test for 12V at pin 8 while in reverse to ensure you have the correct pin before attaching the DRW.
Start your vehicle, select reverse and check you get the result you expect on the camera without producing a trailer lights error.
If all is good, remove the jumper wire.
Remove the right side rear trim and locate the trailer harness connector. It's the rectangular connector at the top in this pic. Identify and confirm the reverse wire with a multimeter. On my vehicle it's a blue wire with an orange trace. Join the DRW to the reverse wire adjacent to the harness connector using a tap method of your choice: posi-tap, solder splice, etc. I would put a 1 or 2 amp fuse inline with the DRW just to be safe. Test again. When you're happy, tidy up and celebrate

--Let me preface that my experience with electricity is VERY limited. (think "Plug and play"). My idea of a multi-meter would be a slide rule and an SAE 'ruler'.

Question: Does this require having the towing option fully enabled/installed? Or just the physical cables installed?

Ordered with the Hitch, so it's "prewired" however is my understanding needs a software update to "fix" (enable something to do with the signal lights.?!)

anand · Jul 18, 2024

flynnsk said:
Question: Does this require having the towing option fully enabled/installed? Or just the physical cables installed?

Ordered with the Hitch, so it's "prewired" however is my understanding needs a software update to "fix" (enable something to do with the signal lights.?!)

The euro wiring outputs are completely different than the US trailer plug, so the above mentioned wiring will most likely not coincide with US trailer output wiring.

With that being said, the reason for that reflash is because the early US towing modules didn't have the correct software installed for the US 7 pin trailer plug.

So the proper answer is that you should have your software updated first, then test with a multimeter to figure out which is the correct reverse trigger on the US models

pernsdorff · Jul 29, 2024

Sure enough.

In my case the wire was the Purple wire. Same position as the above picture though.
NAR differences maybe, or, still going through production stability.

flynnsk · Jul 29, 2024

anand said:
The euro wiring outputs are completely different than the US trailer plug, so the above mentioned wiring will most likely not coincide with US trailer output wiring.

With that being said, the reason for that reflash is because the early US towing modules didn't have the correct software installed for the US 7 pin trailer plug.

So the proper answer is that you should have your software updated first, then test with a multimeter to figure out which is the correct reverse trigger on the US models

Electricity and I, we are polar opposites

.
I traced the harness out the door and up to the rear washer/wiper (activates when go in R). Just need to figure out what wire is what. ("Hey Google, what is a multi meter and how do I use one")

anand · Jul 29, 2024

flynnsk said:
Electricity and I, we are polar opposites .
I traced the harness out the door and up to the rear washer/wiper (activates when go in R). Just need to figure out what wire is what. ("Hey Google, what is a multi meter and how do I use one")

The rear wiper/washer only activates in reverse if the front is on; that's based on a logic output through the body control module

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Reversing light +12v?

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