wiring drl?

I have a 2013 Hyundai Elantra GT, and I just ordered a set of factory LED DRL for lights, they have LED strips inside the for light housing in addition to the typical fog light, here is a picture:


The way I would like to wire them is that they come on with accessory power, and then the shut off if the fog lights are turned on, as there is no reason for it to be on with the fog light, especially since I run yellow fog lights, I think them both on together would look odd.

I am sure something like this would require relays, maybe not? Just looking for the easiest way to wire such a thing. Finding an accessory wire would be easy. Since I installed my subwoofer wires already it would be easy to run my power wire from the interior say off the cig lighter port.

Any advice would be greatly appreciated.

The simplest may be to wire them with +12V to the ACC +12V and the LED GND to the +12V output of the DRL relay. The DRL lights hence provide the GND for the LEDs except when they are on (+12V).

The above assumes that the DRL current is much higher than the LEDs (ie, the DRLs are a much lower resistance than the LEDs).

maybe I worded t wrong, the DRL is the LED..

I want the LED to run with accessory and be on all the time, but when I turn my fog lights on I want the LED to shut off.

Hope that is more clear

No - sorry - I mucked up my answer - I meant FOG instead if DRL... (I think...).

You use the "virtual ground" (bulb) for the LEDs.
IE - with LED+ to +12V and LED- to the bulb's/light's switched +12V, the unswitched/off bulb with GND the LEDs. When +12V to the bulb, there is 0V across the LEDs so they extinguish.


The same technique can be used for any "much higher resistance" aka "much lower current" loads. EG - LEDs or relay coils can be grounded by OFF bulbs.

In practice, current/resistance ratios of at least 5 may work though usually higher than 10:1 is best.
At too low a ratio, the voltage divider effect is significant. EG - at 5:1 across 14V you'd have ~2V across the LED or a small bulb which may light it dimly. And whilst not enough to energise a relay, it may be enough to keep it on.    

Let me see if I am understanding this correctly, as this is above my head haha.. I know + to + and - to - and even know how to wire a single typical relay, but a virtual ground?? haha :D

Hook up the LED (+) to my accessory on power wire, since I want them to be on all the time.

Hook up the LED (-) to the (+) of the fog lights. The (+) of the fog lights acts as a ground when the lights are shut off, so when the lights are turned on the LED is then get a (+) to the (-) side as well as a (+) to the (+) side thus canceling itself out?

If that is correct, its not bad for the LED to have it wired like that, given I have seen no issue with an LED connected backwards for a second or two but say I am driving with my fog lights on for long periods of time, this wouldn't cause any harm? I would hate to burn these LEDs out early.

That is correct.

And it is not "reverse connecting" the LEDs - they have either the normal 12V across them, else 0V - not "-12V".

Only if fogs are on and ACC off would they get -12V, but they should tolerate that since the PIR = Peak Inverse Voltage of a LED is greater than its nominal FWD voltage drop (only old unfiltered AC LED circuits had such reverse breakdown problems).

Use a relay, so when you turn the fog lamps on, it pulls the switch open to interrupt power to your LED DRLs. Basic 5 Pin Mini Relay; Jump a + wire from one of the fog lamps to PIN 85 of the relay, then pin 86 to ground.

Run your ACCY + wire to pin 30 of the relay, then the LED DRLs to 87a. This is the ON position at rest.

When you turn the FOGs on, the coil energizes, and switches to PIN 87 of the relay, opening the connection at 87a, making 87 now the ON position.

powerslave wrote:

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Use a relay, so when you turn the fog lamps on, it pulls the switch open to interrupt power to your LED DRLs. Basic 5 Pin Mini Relay; Jump a + wire from one of the fog lamps to PIN 85 of the relay, then pin 86 to ground.

Run your ACCY + wire to pin 30 of the relay, then the LED DRLs to 87a. This is the ON position at rest.

When you turn the FOGs on, the coil energizes, and switches to PIN 87 of the relay, opening the connection at 87a, making 87 now the ON position.

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Is this what you mean? I am sure I didnt sketch it according to electrical designs, but you can get my idea haha

You only need to splice a wire into a power wire to one of the fogs, and connect it to pin 86. Then pin 85 goes right to a ground. DO not loop the circuit like you have displayed.

Then then yes, ACCY(+) to power the DRLs goes to pin 30, then connect the DRL(+) leads to Pin 87a. Ground the negative sides of your DRLs to any ground.

SO, the relay at rest, power goes to the DRLs when the ACCY wire is hot, and the DRLs illuminate. Then, when you turn on FOGs, the coil is energized, and thus switches (sends the ACCY power) to pin 87. You can use the power at pin 87 to power a Fog Indicator light.