I have installed a led light bar behind the grille of my 2015 RR SC. Its pretty stealth looking and brightens up the road at night when no other car is around!! (Trying not to blind on-comers). I'd like to connect up the wiring harness to come on only when the high beams are on.

I have the Topix wiring layout and do not see any specific wiring for the highbeams. I see a wire for the bi-xenons and then another called the "main beam flap"..others are the DRL, sidemarkers etc. When I test for power @ the wire loom at the headlights, both the bi-xenon and main beam have power regardless of low/high beam.

Am I looking at the right place that will trigger that high beam?

Thx,Will

I think what you need to do is check the voltage on the " main beam flap" wire with the headlights on main beam and then on dip beam. With a bit of luck the voltage will change from +12V to 0V as you switch from one setting to the other.
Depending which way round the voltage changes you should be able to switch either a normally open or normally closed relay to operate your light bar so that it comes on on main beam headlight.
Any chance of posting a picture of your light bar setup?

And welcome to the site.

I have fitted a light bar too and use the flapper motor power to run a 12v spot lamp relay, i found the light bar would start to flash/strobe and eventually knock/trip the LCM out without the relay... A cycle of the ignition would auto correct the LCM but still, be warned the LCM doesn’t like powering too much extra stuff

How soon would the light bar start to flicker? was it after it was on for some amount of time? or was it from the relay going on and off (like if you have your lights on auto high)??

Just wired everything up and then so your post on the LCM.....just trying to figure out what they symptoms look like and perhaps its not a good idea to run off the high beams!!

Thx,Will

I have to agree with Craig re using a relay. I personally wouldn't connect any additional bits to these cars without using a relay. I use a relay switched from the flap wire to switch a light bar without issue to date.

Mine is connected the same way. Connecting to the main flap is just to trigger the relay....the main battery is powering the actual light bar! Thx again for the help!

The light bar would start to flicker around 30 seconds after start up WITHOUT using a relay, it would then knock the LCM out 10-20 seconds later...

A quick thought, how do you wash your light bar if its behind the grille?

I swapped out the grille and put in a different one to let more light through....as far as keeping the bar clean, I guess you just spray thru the grille? Too much of a pain to get the grille out each time....

So far so good with the wiring to a relay, have the lights set for auto and the high beams are coming on and off as expected!!

Took a pic of the bar also while the grille was off....

This is something I intend to do. And I also want to use a 433mhz key fob, so I can then program this into my garage door opener in the car, giving me a stealth but still oem on off source inside the car.

It's a shame you can't code the car with the IID tool so that the front fog lights come on with main beam, because then I would take a feed direct from the fogs and run 2x light bars all behind the grill and each powered by a fog light. As a side note I was also thinking to remove the headlights and drill out a hole in the dummy (empty) reflector and use a pair of H7 LED main beam bulbs 160w each and make use of the reflector like the old L322 had the extra main beam

Do you know if this is possible?

Wow, I like the look of that, is this an upgrade you offer Craig. letters not necessarily in the right order

Can anyone definitively help with what wire is needed to trigger? I have a huge flaw in my 433mhz build... while it works perfectly, I massively underestimated the interference potential from other 433mhz items... I.e. at work when they open the compound gates it's triggering my light bar, and I've had reports of a disco coming from behind my grill during the day.

Can someone tell me what pin or color wire I need to use from the headlight? I am using a relay system so no issue with that.

Better yet I would prefer it on the fog light switch!

I have figured this out by taking the plug off and using a volt meter to watch for a volt jump.

Turns out there is 1 cable blue with a green stripe, and this sits at 1.30V and jumps to 12V or 14v with engine running. Perfect! Wired in and done now