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DRL Operation w/ Headlights On

77301 Views 243 Replies 67 Participants Last post by  rjcalif
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This isn't an exact how-to on getting your DRLs to operate with headlamps, but more of a resource on how I did it on my own car.
I believe there are multiple ways of accomplishing this, for example, reprograming the BCM, but for me this was cheapest/easiest solution for me.


The materials I used were; 1 single pole double throw 15 amp relay, breadboard, wire, heat shrink, solder (soldering iron), and 1 eyelet connector.


So, if you look at the attached headlight and DRL wiring schematic, it is seen that the BCM provides power to both DRLs via a violet with green stripe wire.


My idea was to use a spdt relay to switch from BCM power to power provided to the headlamps from the low beam relay. The first attachment illustrates this. Basically, when the electromagnet of the relay is NOT energized, the relay maintains a connection between the BCM and DRL LEDs. When the electromagnet becomes energized, the relay then switches to the other contact and completes a circuit between the DRL LEDs and the voltage supply to the head lamp HIDs.


The second attachment shows the location of the two wires you'll need access to. The headlight voltage supply, yellow in color, and the BCM V+, violet with a green stripe. There are two yellow wires inside of the loom, one is for the right headlight and the other for the left. Either one will work for our purpose.


The fourth attachment shows the connections being made in series between the BCM and DRLs.


The last attachment shows the connection to the headlamp voltage supply wire and ground.


The fifth and sixth attachments show the spdt relay soldered to the bread board with the wire connections. I did place this inside of a sealed project box to protect it from the elements, but I forgot to take picture of that.


Lastly, the seventh attachment is a picture of my car with both the Headlights and DRLs on at the same time.


If you guys have any questions, concerns, or comments please fire away.

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I purchased everything from RadioShack, but I'm sure you could have a good audio shop fab everything up for you.
I purchased everything from RadioShack, but I'm sure you could have a good audio shop fab everything up for you.
Looks like you did such a great job you might be able to turn into a little side business...Great work and I'm sure cost would not be an issue then you can take the board to stereo shop for final installation...
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I'd rather try to help people then make any money from this.
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Just a quick update, everything is still operating as intended and if a failure does come up, I'll post the cause and solution.

Very impressive.


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Thanks.
MacGyver could learn a thing or two from DangChung!
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This would be easier for the layman to use a cube relay.
87 and 86 to the yellow head light wire.
85 to ground.
30 to day time running lights. Violet with green stripe.
87a to output from BCM. Violet with green stripe.
If you run a three conductor wire into the cab you can install the relay under the dash to keep it out of the weather. I'm sure a ground can be found under the dash somewhere.
Thanks for identifying the wire colors and location.
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This would be easier for the layman to use a cube relay.
87 and 86 to the yellow head light wire.
85 to ground.
30 to day time running lights. Violet with green stripe.
87a to output from BCM. Violet with green stripe.
If you run a three conductor wire into the cab you can install the relay under the dash to keep it out of the weather. I'm sure a ground can be found under the dash somewhere.
Thanks for identifying the wire colors and location.
Here's a link to a relay that Rottster is referring to. Buy Factory Air Air Conditioning Relay 35928 at Advance Auto Parts

This would be a more robust and serviceable alternative to what I've done and I would've gone this route if I could've located one. I was a little impatient, so I purchased what I could find at the time.

I would be a little cautious on a installing under the dash due to the generated em fields from the relay and wires during switching events. It could possibly generate false signals on CAN bus or any other data wires if inadvertently placed near one.

And if anyone is wondering, everything is still operating as intended.
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I've done this before on another car. How much watts is going to the DLR?

Get a resistor that matches the draw of the DRL and connect the resistor to the stock circuit in place of the stock DRL.

This should trick the computer into thinking you have working DRLs

Now run a regular HID relay to the DRLs direct from the battery and run a switch to your dash.

You will have full control of the DRLs even if the car is off.

Would that work?
It should work.

I'm not sure on the power consumption but I do know the BCM supplies battery voltage. You could measure for current draw and use this equation to determine power, power= voltage x current. Just be sure to the same size units.

Once find the power you can determine the needed resistance with Resistance = (voltage^2) / power. Just be sure to buy a resistor at the rated power you calculated.
All I can say, is the end result looks great! If I could just hook a couple wires together that would be great .....you lost me on all this, but really cool look. **** I wish I could be that smart :)
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All I can say, is the end result looks great! If I could just hook a couple wires together that would be great .....you lost me on all this, but really cool look. **** I wish I could be that smart :)
If I have time this weekend I'll purchase a relay and some female connectors to illustrate how you would wire up a cube relay. You could always look into a local car stereo shop to help with the install. There should be enough information in my first post and Rottster's post for them to do it. If you have any questions, don't hesitate to ask.
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Hella makes one of the best cube relays and it's water proof. Amazon sells it and you would need to pick up the plug with it. Both cost about $20 + shipping. Best part, when installed and mounted it would look factory installed. Be sure to use heat shrink type connectors, not just black tape. The coper wire would corrode and your lights would stop working if not properly protected. I would put a link to the relay but I'm not link smart on my iPad.
DangChung would you do it for me?
You are an asset to this forum, keep up the great work!
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Hella makes one of the best cube relays and it's water proof. Amazon sells it and you would need to pick up the plug with it. Both cost about $20 + shipping. Best part, when installed and mounted it would look factory installed. Be sure to use heat shrink type connectors, not just black tape. The coper wire would corrode and your lights would stop working if not properly protected. I would put a link to the relay but I'm not link smart on my iPad.
DangChung would you do it for me?
You are an asset to this forum, keep up the great work!
I was just looking on Amazon, they have a lot of Hella relays listed. Which one would I be looking for ? Thanks for your help you guys.
007794301 is the number for the relay on Amazon. Scroll down to see the frequently bought together and you will see the weather proof plug. No fuse will be needed for this installation.
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007794301 is the number for the relay on Amazon. Scroll down to see the frequently bought together and you will see the weather proof plug. No fuse will be needed oft this installation.
Great find!

HELLA 007794301 Weatherproof 20/40 Amp SPDT Mini Relay with Bracket:Amazon:Automotive


HELLA H84709001 Iso Weatherproof Relay Connector with 12" Leads:Amazon:Automotive
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This is fabulous, just ordered both. May need guidence on how to hook up, I'm good at tracing wires and installing stereos, I'll just need to know where to look. Thanks again, we'll have the some Bad Ass looking ss's:eek:ccasion14:
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its a nice look

have all the lights on at the same time :D
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