Clean LED DRL and Parking Light Modification (Without Resistors)

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Re: Clean LED DRL Modification (Without Resistors)

Post by se4njb7 » Wed Jan 13, 2021 9:15 pm

Another few questions... so what would happen if you put the incandescent bulbs in the drls with the ecu resistor mod? Do you think you would fry the ecu? And with the parking lights does changing the resistor work on the uk/European models and for a saloon?

I’ve got another ecu here ready to mod haha

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Re: Clean LED DRL Modification (Without Resistors)

Post by se4njb7 » Wed Jan 13, 2021 9:16 pm

And you should be able to change the vin number in the coding or adaptation 👍🏽

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Re: Clean LED DRL Modification (Without Resistors)

Post by dr.electron » Sun Feb 07, 2021 8:07 pm

Apologies for the late reply, here:
Another few questions... so what would happen if you put the incandescent bulbs in the drls with the ecu resistor mod? Do you think you would fry the ecu? And with the parking lights does changing the resistor work on the uk/European models and for a saloon?
I don't believe it will hurt anything if you run incandescents with this mod in place, because the smart switch IC drives a scaled-down current through the sense resistor. At worst, the BCU might give an error thinking that the current was too high, but I don't see anything getting damaged. And if I'm wrong, it's the BCU that would be damaged, not the ECU. I don't know for sure if the mod will work in Europe, but I don't see any obvious variations in the wiring diagram that suggest alternate DRL connectivity.

For what it's worth, I ran incandescent parking lights for months with a mod in place for LEDs, and there were no ill effects.
Last edited by dr.electron on Sun Feb 07, 2021 8:42 pm, edited 1 time in total.

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Re: Clean LED DRL and Parking Light Modification (Without Resistors)

Post by dr.electron » Sun Feb 07, 2021 8:39 pm

I've updated my original post to include the modifications for using LED parking lights, which I now have working on my RS4.

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Re: Clean LED DRL and Parking Light Modification (Without Resistors)

Post by se4njb7 » Mon Feb 08, 2021 4:02 pm

dr.electron wrote:
Sun Feb 07, 2021 8:39 pm
I've updated my original post to include the modifications for using LED parking lights, which I now have working on my RS4.
Okay sounds good then. Read your post and I’m just wondering what are the resistors you ordered for the parking lights etc so I can order them too. The 0805 resistors look physically bigger than the parking light ones. Cheers!

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Re: Clean LED DRL and Parking Light Modification (Without Resistors)

Post by Brooner » Mon Feb 08, 2021 4:46 pm

i used PAA bulbs not LED but give a nice white light so cleans up the front headlights

https://audisrs.com/drl-s-finally-changed-t7621.html
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Re: Clean LED DRL and Parking Light Modification (Without Resistors)

Post by dr.electron » Mon Feb 08, 2021 8:59 pm

se4njb7 wrote:
Mon Feb 08, 2021 4:02 pm
dr.electron wrote:
Sun Feb 07, 2021 8:39 pm
I've updated my original post to include the modifications for using LED parking lights, which I now have working on my RS4.
Okay sounds good then. Read your post and I’m just wondering what are the resistors you ordered for the parking lights etc so I can order them too. The 0805 resistors look physically bigger than the parking light ones. Cheers!
Excellent observation - the parking light resistors are 0603 sized. I'll add that to the original post, along with links to some example parts.

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Re: Clean LED DRL and Parking Light Modification (Without Resistors)

Post by dr.electron » Mon Feb 08, 2021 9:05 pm

Brooner wrote:
Mon Feb 08, 2021 4:46 pm
i used PAA bulbs not LED but give a nice white light so cleans up the front headlights
Oh wow - those do look nice. And they don't require any modification, which is definitely a bonus.

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Re: Clean LED DRL and Parking Light Modification (Without Resistors)

Post by dr.electron » Tue Feb 09, 2021 12:51 am

After two days (and nights) of driving around with the parking light mod in place, I got an error for the right light when I started the car this evening. Went to the store, and when I started the car after shopping, there was no error. Since this is clearly marginal on failing, I’m going to change that 20kohm resistor to 30.1kohm, to provide some more buffer. I’ll update the initial post to reflect this, and will make the change to my car later tonight.

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Re: Clean LED DRL and Parking Light Modification (Without Resistors)

Post by dr.electron » Tue Feb 09, 2021 2:01 am

Swapped out the 20kohm for 30.1kohm, and no errors. Of course, I didn't have any with the 20kohm for the rest of this evening after the first one....I suspect that I got the first one because the board was cold after sitting all day. So it was really close to working/failing. 30.1k should work no problem.

Good news is that I'm getting really good at pulling the BCU. I didn't even disconnect the fuse blocks - just took the board out while leaving the housing attached to them. I did still have to disconnect the harnesses, of course. This time it took 20min from start to finish, including the soldering. For those of you who've never soldered little surface-mount parts before, and don't have tweezers and a soldering iron with a small tip, that will probably be the trickiest part. After that, removing the fuse blocks is the biggest hassle - which is why I pulled the board in the car.

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Re: Clean LED DRL Modification (Without Resistors)

Post by dr.electron » Tue Feb 09, 2021 2:12 am

dhali wrote:
Sun Nov 29, 2020 7:04 am
WoW !! .Well done for having an indepth look into this . Does this BCM control the rear number plate lights from here aswell ?
They seem to cause issues too when swapping to Leds bulbs .
As I now note in my modified original post, I think that changing resistor (1) in the parking brake mod will allow this, if I'm reading the wiring diagram correctly. If it doesn't work, it may be that a larger resistor will work - like 15kohm or 20kohm.

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Re: Clean LED DRL and Parking Light Modification (Without Resistors)

Post by dhali » Tue Feb 09, 2021 10:52 pm

Nice one . Thanks for the update

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Re: Clean LED DRL and Parking Light Modification (Without Resistors)

Post by se4njb7 » Fri Feb 12, 2021 8:18 pm

I have ordered 20kohm and the 30kohm resistors for the mod. I have led bulbs in the number plate lights so can test if that works. Currently have resistors in place to stop the number plate errors. Hopefully can test during next week.

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Re: Clean LED DRL and Parking Light Modification (Without Resistors)

Post by se4njb7 » Fri Feb 12, 2021 8:19 pm

And I have already soldered the DRL resistors so just a case of waiting for the parking/number plate mod resistors and I will know if it works for the UK vehicles

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Re: Clean LED DRL and Parking Light Modification (Without Resistors)

Post by dhali » Fri Feb 12, 2021 9:49 pm

se4njb7 wrote:
Fri Feb 12, 2021 8:19 pm
And I have already soldered the DRL resistors so just a case of waiting for the parking/number plate mod resistors and I will know if it works for the UK vehicles
Great !! .Look forward to the update

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