Hi-beam trigger for light bar relay?

[YotaGoat]

I finally received my SSO front bumper and will be installing it with a 30" Baja light bar. My preference is to not have a separate dash switch for the light bar and just have the light bar relay trigger when the hi-beams are turned on.

I did a quick look at the wiring going into the headlights and there are only 2 wires. Does anyone have any suggestions for where I can pick-up the power wire that turns on the hi-beams?

 

[fkheath]

I did a quick look at the wiring going into the headlights and there are only 2 wires. Does anyone have any suggestions for where I can pick-up the power wire that turns on the hi-beams?

Since the high beams also double as the DRL (daytime running lights) you cannot use the wires to the headlight for the light bar trigger.

 

[YotaGoat]

Thanks for the reply. That's why I like my '70's vintage vehicles... everything is simple.

 

[PJSnow]

Here is a thread discussing the high beam trigger and the PWM signal from the DRL. Simple solution for you might be a low voltage cutoff module.

Auxiliary high-beam tap to relay, lights flickering in DRL mode | Toyota 4Runner Forum [4Runners.com]

 

[YotaGoat]

Here is a thread discussing the high beam trigger and the PWM signal from the DRL. Simple solution for you might be a low voltage cutoff module.

Auxiliary high-beam tap to relay, lights flickering in DRL mode | Toyota 4Runner Forum [4Runners.com]

Thanks for the link PJ, definitely interesting but simplicity is my friend and reaching to the dash to press a switch is no biggie for me. We live in the remote mountains of CO so not lots of traffic on the roads at night (at least not cars, lots of wildlife) so it won't be lots of switching on and off.

 

[hoppyjr]

Why not install a harness with relay and switch, then trip the circuit with the high beam. You could leave the switch in “on” position and the bar would activate with high beams, but you’d have the option of keeping the bar off by a press of the switch.

 

[Bombguy]

Why not install a harness with relay and switch, then trip the circuit with the high beam. You could leave the switch in “on” position and the bar would activate with high beams, but you’d have the option of keeping the bar off by a press of the switch.

This would also be a good choice as in many areas the light bar is not street legal, and is actually a safety hazard for road driving.

 

[YotaGoat]

Why not install a harness with relay and switch, then trip the circuit with the high beam. You could leave the switch in “on” position and the bar would activate with high beams, but you’d have the option of keeping the bar off by a press of the switch.

This would also be a good choice as in many areas the light bar is not street legal, and is actually a safety hazard for road driving.

Guys, this was my original intention and question but it seems that there is a pulse signal that controls the high beams and would not play nice as a trigger for the relay without some custom circuitry that I'm not interested in building. If you guys know differently please let me know.

In my neck of the woods street legal is a pretty short, basic list of requirements. There are more cattle, deer and elk than people and there is no state inspection like in the east so no one to tell me what I can and can't do.

 

[hoppyjr]

Guys, this was my original intention and question but it seems that there is a pulse signal that controls the high beams and would not play nice as a trigger for the relay without some custom circuitry that I'm not interested in building. If you guys know differently please let me know.

In my neck of the woods street legal is a pretty short, basic list of requirements. There are more cattle, deer and elk than people and there is no state inspection like in the east so no one to tell me what I can and can't do.

I think the wires at the bulb end have first run through the controller that manages the DRL / High function, through the BCM. Your best bet is to grab the high beam signal at the interior fuse box, after the high beam switch and before the BCM.

 

[YotaGoat]

I think the wires at the bulb end have first run through the controller that manages the DRL / High function, through the BCM. Your best bet is to grab the high beam signal at the interior fuse box, after the high beam switch and before the BCM.

If this is correct that would certainly work. However, I'm questioning the location of the high beam fuse. Aren't they located in the fuse box under the hood (fuses #15 & 16)? Is this point definitely before the DRL controller?

I could wire up a test of the circuit but it would be good to know in advance if this is potentially a problem to pick up the signal from there.

 

[PJSnow]

If this is correct that would certainly work. However, I'm questioning the location of the high beam fuse. Aren't they located in the fuse box under the hood (fuses #15 & 16)? Is this point definitely before the DRL controller?

I could wire up a test of the circuit but it would be good to know in advance if this is potentially a problem to pick up the signal from there.

The high beam fuses are inside the engine bay as you described. They are downstream of the DRL relay and the BCM (after the PWM signal input). There is a thread somewhere questioning if the PWM comes from the DRL relay (costs over $200) or if the BCM creates the signal, but this has yet to be determined.

The only way to confirm the PWM signal is with an oscilloscope (or potentially a high end multimeter?), neither of which I have access to. But based on the other thread I linked previously, connecting to the high beam fuse will cause buzzing/flickering of the relay (first hand account of the OP on that thread).

I did measure the voltage at the high beam fuse for different scenarios:
1. Vehicle off, 0.05V
2. DRL on, 9.6V
3. High beam on, 12+V

The 9.6V from the DRL was enough to trigger a simple automotive relay regardless of the PWM signal. Since there appears to be no rules where you are, I don't expect occasionally flashing your auxiliary lights while in DRL mode will be an issue. I would suggest picking up a low voltage cutoff module/relay (LVC) which will only pass power through on the higher voltage from the high beams. You should still run this signal to the 85 pin on a normal relay because I don't think the LVC can take the current of a light bar. The LVC is basically replacing the dash switch that you want to avoid.

 

[YotaGoat]

I would suggest picking up a low voltage cutoff module/relay (LVC) which will only pass power through on the higher voltage from the high beams. You should still run this signal to the 85 pin on a normal relay because I don't think the LVC can take the current of a light bar. The LVC is basically replacing the dash switch that you want to avoid.

I like this as a simple, prebuilt solution. I'll just need to enclose it to weatherproof the PCB which shouldn't be an issue. Looks like its preconfigured for 10.5v so should be good right out of the box. Also, agree with you on the relay wiring as I always isolate the trigger from the line voltage to the lights. Thank you!

 

[PJSnow]

I like this as a simple, prebuilt solution. I'll just need to enclose it to weatherproof the PCB which shouldn't be an issue. Looks like its preconfigured for 10.5v so should be good right out of the box. Also, agree with you on the relay wiring as I always isolate the trigger from the line voltage to the lights. Thank you!

This is the project box I was planning to get to enclose mine. I might size up/down depending if I want to fit the PWM filter in there or not. You might be able to use a slightly smaller box for just the LVC module or you can size it up to squeeze a relay inside.

 

[YotaGoat]

You rock PJ. I'll post some pictures and feedback once I get the bumper on and lighting wired up.