Light bar on/off with high beams (1 Viewer)

[Clyde S Dale]

I'm looking to install a slim light bar in my lower grill area of my 2011 LX570. I want to install a 3 position switch so I can wire one side to be a simple on/off, but I want the other position to only activate the light when my high beams are on. I am thinking to pull a signal for the 2nd relay off the high beam, but does anyone know if they are switched by the positive or the negative side?

 

[lx200inAR]

I couldn’t find it, but I know the circuit diagram for the high beam/DRL is posted on forum. It’s fairly convoluted. I believe there were 3 relays, because the truck switches the high beams from a parallel circuit to a series circuit when in DRL mode. I suspect none of this matters, if you are just trying to tap the high beam relay signal.

Im not a 12v expert, but seems like if you pulled a high beam plug while lights are off, you could check for continuity between ground and plug. If neither leg has continuity, then ground switched. Although checking at the plug, doesn’t necessarily mean that is how the relay is triggered.

 

[kcjaz]

Aren’t there DOT or other laws/regulations that limit when accessory lighting comes on? The functionality you are going for makes sense. I want my fogs on with high beams but the factory doesn’t do that without modification. I think all OEM fog light circuits are like this due to regulation. Not sure how light bars are viewed in this regard. I sure drive into a lot of other peoples light bars on with there low beams.

I am on a lot of lonely country two lane roads (lots of deer) and would like all my lights on at times with the ability to drop down to factory low beam using the factory column switch.

 

[Clyde S Dale]

Aren’t there DOT or other laws/regulations that limit when accessory lighting comes on? The functionality you are going for makes sense. I want my fogs on with high beams but the factory doesn’t do that without modification. I think all OEM fog light circuits are like this due to regulation. Not sure how light bars are viewed in this regard. I sure drive into a lot of other peoples light bars on with there low beams.

I am on a lot of lonely country two lane roads (lots of deer) and would like all my lights on at times with the ability to drop down to factory low beam using the factory column switch.

That is exactly why i want to wire it this way. The light bar is not DOT legal and I do not want to blind any oncoming drivers, but I could use the extra light to avoid deer and pigs on back roads.

 

[CharlieS]

Not sure if this is helpful, but Stedi sells a plug in harness that goes inline - it has a high beam trigger wire coming out of it - combined with their light harness, it makes the aux lights only come on if your high beams are on. You could easily use it to trigger a relay to do what you are trying to do. I think it was $20 or so.

 

[Moby]

I've done this with multiple vehicles, incuding my 200. Use a fuse tap on the stock high beam fuse. Run the fuse tap wire to your light bar switch input. Then switch output to relay input. Ground the relay. Battery power to relay input and relay output to light bar. Ground the light bar.

This way if you turn the light bar switch on without the high beams nothing happens - the high beam fuse isn't flowing current so your switch does nothing. Turn the high beams on with the light bar switch off and you just get high beams. Turn the light bar switch on and then turn the high beams on and you'll get both.

Works really well when you are on a dark highway in the middle of the night where you need a lot of light but can easily turn off both from the stock high beam switch to avoid blinding someone.

Edit - you can easily adapt this to a three position switch.

 

[TeCKis300]

There's some discussion in this thread which might give you a few more ideas on how to do it.

Switch Panel / Switchpros Install Underhood Tap Points

Lots of people have installed these but I couldn't find a good reference as to where to tap for various things underhood. Here's my attempt to document some of the more common taps and triggers. Including a much wanted stock fog light override function. I'm using a 1/4" gland fitting to route...

forum.ih8mud.com