DRL Tail lights always on (Research and development!) - Civinfo
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post #1 of 8 (permalink) Old 21st May 2019, 18:55 Thread Starter
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Tail lights always on (Research and development!)

Thinking back to the Pre facelift, I remember some jumper wire hacks that would allow the DRLs to remain on with headlights.

Now, I'm wondering if it would be possible to do the same with the post facelift - To have tail lights on with DRLs; both for looks and improved rear visibility.

I've got the exterior lights wiring diagram (Attached), which I'm poring over at the moment - That being said, it's the internet, so someone better at electronics than me is certainly out there.

Any ideas of where a jumper wire / resistor / anything could be added to have tail lights with DRLs active?

I'm mostly looking at the DRL / Taillight relay as a best bet at the moment.
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File Type: pdf 9G Exterior Light Circuit Diagram.pdf (814.0 KB, 15 views)
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post #2 of 8 (permalink) Old 21st May 2019, 20:25
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Looking at the Cct., an instant problem arises. The DRLs are used as both DRLs and the front position (side) lights.
When you switch on the lights, the tail lights come on. The tail light voltage is applied, via Fuse C34 and the red wire to pin 1 of the DRLs . (Presumably, point C goes to the actual tail light bulbs. Best I have a look at the other sheets of the pdf) This connection presumably switches the DRLs to low intensity when you switch the lights on. (By design and Law.)

So any time the tail lights are on, either by you switching them on, or a frig, the DRLs will be on low intensity so that the tail lights and the dimmed DRLs will act as position (side) lights and the DRLs, being dim, will not act as DRLs. This is a 'closed circuit loop' that has to be broken to get the tail lights on with the DRLs on full intensity until you switch on the lights.

So the solution to the problem is not as easy as it first seems. And I don't have one that would fully comply with the law. But I'll think about it as you are not the first person to ask about this, and it makes so much sense that I'm surprised that they were not designed that way in the first place. Having said that, a theoretical solution might not be possible/practical to implement.
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post #3 of 8 (permalink) Old 21st May 2019, 20:44 Thread Starter
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I was hoping you'd hop along. Electrician by trade?

I've not touched it since A level physics

That makes sense.

I've highlighted the diagram for my own benefit...




Not that I have much more than a figment of an idea what I'm looking at

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post #4 of 8 (permalink) Old 21st May 2019, 21:27
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Simple solution to the problem, turn the lights on every time you get in the car. Job done, lights on at the front, lights on at the rear. No messing around with wiring.
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post #5 of 8 (permalink) Old 21st May 2019, 21:28 Thread Starter
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A simple solution, and one that I've employed up until now - However, With sidelights, it's a little too dim for daytime use, and headlights + DRLs don't look as cool as DRL's alone
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post #6 of 8 (permalink) Old 21st May 2019, 22:19
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Quote:
Originally Posted by Das View Post
Simple solution to the problem, turn the lights on every time you get in the car.
Not simples. DRLs will not be on bright.

1. Cut the red wire to the tail/number plate lights.
2. Connect the end of that wire that goes to the tail/number plate lights to one of the light green wires that goes from the DRL relay to the DRLs.
3. Possibly change the fuse associated with DRLs (C37) from 7.5A to 10A.

Now the tail lights will come on when the DRL relay energises and they come on. The DRLs will still dim when you switch the lights on via the Taillight relay and pin 1 on the DRLs as per normal.

Much easier said than done no doubt.
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post #7 of 8 (permalink) Old 21st May 2019, 22:46 Thread Starter
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I knew you'd get there eventually

Not quite the jumper wire I was hoping for, but one to ponder on!

As you'd expect, I'm dubious of cutting into looms - Will need to figure out where they are in practice, too!

I'd imagine a join would need to be somewhere in the engine bay, probaby on the wiring coming out of the front fuse box.

----

I've just reviewed the diagram once again; and I've noticed - The red wire goes to both headlights; to the tail lights. Intrestingly, when my front right daytime running light failed ("Ballast" / LED Driver issue?) there were no issues with the tail lights. I wonder how the power supply operates with the rear lights? would probably be more cost effective to run them from the headlight drivers (Seemingly on one at a time)

Anywhom, as the wire runs to both headlights, it may be much easier / possible to jump the wires at the connector.
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post #8 of 8 (permalink) Old 21st May 2019, 22:58
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No the red wires go to the tail/plate lights and the DRLs not the headlights (Ah, I see. You meant the headlight unit). I am assuming that this latter connection (red to DRLs) has the effect of dimming the DRLs when you switch on the lights and the tail lights come on. The main DLR current will come from the DRL relay via the LT GRN wires. Which is why I suggested that the red to the tail lights be connected to the LT GRN.

Yeah, it probably would be easier, as you say, to tap into the LT GRN as it goes into a headlight unit, cut the red in the tail light area somewhere and run a new wire front to back (insulating cut end of red).

Now I have seen just how difficult/warranty destroying it is, I give up on mine.
Perhaps it would be possible to pull the red wire connector out of a plug/socket somewhere around the tailgate area rather than cutting the wire?
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