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Wiring Light Bar into High Beams


TroyButler
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General question for those who know there pathy/QX4 and wiring better than I. So the switch that came with my light bar broke, and i dint want to completely waste it, so i chopped up the harness and connected it directly to my highbeams, so the stock on my steering wheel controls the lights now. My problem is as follows:

 

Headlights on: light bar off

Head lights on + High beams: Light bar on

Even the momentary switch works.

Head lights off: Light bar on.

 

Anyone know why with the head lights off the light bar is on? Until i turn the car off, then the light bar is off.

 

Thank you.

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20 minutes ago, D_Bomb17 said:

Daytime running lights. They are actually your high beams at half brightness that come on when the headlight switch is off. 

Damn. I thought it would be the low beams. Anyway to work around that, and have it trigger with just he high beams and not running lights? 

 

Im currently tapped into the high beam wire if that matters.

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I believe you'll need a resistor and a relay to accomplish your goal. The DRL voltage is usually quite low, somewhere between 3 and 6 volts. (Use a voltmeter to check the DRL voltage.) If you tap into the high beams for your light bar, the DRL voltage is still high enough to trigger the lights. You need to add a resistor between the high beam wire and your automotive relay so that the relay will not trip until it gets enough voltage. The size of the resistor will vary based on the relay's "ON" voltage and the DRL circuit's output voltage.

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Another solution would involve adding a second relay connected to the parking lamp circuit. So, you'd have to have both the parking lamps on and the high beams on in order to activate the light bar.

 

Note: this solution applies only if the DRL circuit uses a switched POSITIVE signal, rather than a switched GROUND signal. Use a multimeter to check the circuits.

 

I'll assume that the light bar came with its own relay. Remove the relay signal wire (probably 85 or 86) from the high beam circuit where you've attached it already.

The light bar relay should be rewired as follows:

30: to battery +12vDC

87: to light bar

85: to new relay terminal 87

86: to ground

 

Wire the new relay as follows:

30: to high beam circuit

87: to light bar terminal 85

85: to parking light circuit

86: to ground

 

Edited by XPLORx4
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2 hours ago, XPLORx4 said:

I believe you'll need a resistor and a relay to accomplish your goal. The DRL voltage is usually quite low, somewhere between 3 and 6 volts. (Use a voltmeter to check the DRL voltage.) If you tap into the high beams for your light bar, the DRL voltage is still high enough to trigger the lights. You need to add a resistor between the high beam wire and your automotive relay so that the relay will not trip until it gets enough voltage. The size of the resistor will vary based on the relay's "ON" voltage and the DRL circuit's output voltage.

Thats a really good idea thank you. I was just gonna pull a fuse for DRL and see if that worked, but now i have an option A and B?

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Another approach would be to use the high beam wire near the switch to trigger the light bar. That is upstream of the drl module and won't trigger the light bar relay.

 

You could also just get another switch, they are cheap. Would also protect you from official attention since it is illegal to operate a light bar on public roads in most places. Just wire it in so that it prevents the light bar from  turning on unless you want it on with the high beams. 

 

The factory or dealer installed foglights in my path were wired this way, but triggered with the low beams. I didn't like that set up, so moved the trigger to the park lights so I could run the fogs without the headlights, a more desirable setup in heavy snowstorms. At least it did back when we had heavy snowstorms here...

Edited by Mr_Reverse
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On 9/4/2019 at 7:38 PM, Mr_Reverse said:

Another approach would be to use the high beam wire near the switch to trigger the light bar. That is upstream of the drl module and won't trigger the light bar relay.

 

You could also just get another switch, they are cheap. Would also protect you from official attention since it is illegal to operate a light bar on public roads in most places. Just wire it in so that it prevents the light bar from  turning on unless you want it on with the high beams. 

 

The factory or dealer installed foglights in my path were wired this way, but triggered with the low beams. I didn't like that set up, so moved the trigger to the park lights so I could run the fogs without the headlights, a more desirable setup in heavy snowstorms. At least it did back when we had heavy snowstorms here...

The reason i was trying to go this route mainly was to prevent trying to run wires into the cabin. I liked the resistor idea, but then it would be a lot of guessing buying resistors since i dont know what the required voltage is to trigger the relay. Wiring is by far not my specialty. I also learned there is not a fuse for just the DRL, so i was trying to just cut a wire to disable them but boy is that a whole process. Cut the driver side high wire to the DRL module and all that did was eliminate my driver side high beam, still had running lights, loose my high beam dash indicator, but there was like a 1 second delay and my light bar still worked so something else must still be triggering it with enough power?

 

Also: soldering between the battery and the fender to get the tiny wires for the DRL is a pain - do not recommend.

 

PS PS: I do appreciate all the potential solutions, im just not smart enough to implement all of them i was happy enought just to make a working wiring harness, and cutting a wire is very simple, once you know the correct wire

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