BMW R1200RT/R1250RT Forum

LED masochism continues...

I put on a 50W (?) resistor on the line BEFORE the two LED bulbs.
CanBus did not like that!

I've ordered smaller resistors 10W (?) thinking that maybe 50W resistance is way too much!
It dims all the lights that come after it along the brake light wire quite a lot!

if two filament bulbs resist 50, then replacing them with LED bulbs that resist 30 should require a resistor that resists 20 to get the overall resistance back up to 50.

At that point, CanBus doesn't know that anything changed. It can't. The resistence is now identical.

I'm guessing that's how this works.

Getting the right mix of LED/Resistor that EQUALS the original filament resistance seems to be the goal.

As the brake light electricity flows, one way, down stream, the resistor has to appear first BEFORE the two LED brake lights. (??? does it?)

Is the resistance CanBus sees aggregated?

Is the perceived resistance RESISTOR+LED+LED?

or simply Filament Bulb+Filament Bulb? (as it was in the beginning?)

It seems like you'd have to know a precise resistance for each element to get it to equal the original number.

Maybe that's the game?

I appreciate those who suffer these posts.
Thank you for that kind of patience...

We learn by doing....

The two brake / tail lights are wired in parallel. When replacing one 21W filament bulb with a LED + resistor, it may be best to add the additional resistor in parallel, close to each bulb holder. (This is how it is shown to be done in the video on page 4).

Putting a resistor in series, in the common supply to the two brake / tail light bulb holders will, as experienced, dim both bulbs.

In parallel, the two 21W filament bulbs (at 12v) have an effective resistance of 3.43 ohms. This is what the CAN-bus system needs to see in that circuit. The additional resistor was fitted in series with two LED bulbs in parallel, therefore, is it not a simple case of adding all three resistances together. This is true if all resistors are in series but they are not.

What is the wattage (W) and/or the resistance (ohms) of each LED bulb.

How about asking the LED bulb manufacturer for advice. They may be able to suggest/supply a resistor kit to work with their bulb. Again, this is what is shown in the video.

In the UK, have spoken to ABD, https://www.autobulbsdirect.co.uk/

Their advice is to find a LED bulb which doesn't throw a CAN-bus error. They are going away from using resistor kits, this being the one used in the video, https://www.autobulbsdirect.co.uk/canbu ... l1011.html 21W now out of stock.

Alternatively, they are now offering Twenty20 LED bulbs, https://www.autobulbsdirect.co.uk/382-p21w-led-bulbs/ If the first one throws up a CAN-bus error, they suggested trying the CanPlus bulb. If the bulbs don't work, they offer a replacement or refund.

Another UK supplier, https://www.ledperf.co.uk/led-bulb-for- ... 12946.html shipping worldwide.

Customer review

"Works well, very bright, to see over time. No error on the ODB. It's perfect 20/20."

David. wrote: ↑Fri Jan 10, 2025 11:51 am Another UK supplier, https://www.ledperf.co.uk/led-bulb-for- ... 12946.html shipping worldwide.

Customer review

"Works well, very bright, to see over time. No error on the ODB. It's perfect 20/20."

They are actually in France, just with a UK domain "LEDPERF SAS CS 30237 42408 SAINT-CHAMOND CEDEX FRANCE"
https://www.ledperf.co.uk/qsn.php

Other than the colour (amber), the indicator filament bulbs are the same 21W as the tail/brake (clear).

As the AUXLIGHT LED's have been successful in the usually fussy indicators, do AUXLIGHT offer a red LED for the tail/brake.

as always l wish I'd known that two months ago!

Everytime d have a problem like this, I say to myself " I am not the first person....".

I will order the 20 20 (?) bulbs and try that. I can add them to the bag of 20 or so bulbs I already have should they not work

Thank you, gentlemen.

- - - - -
Wow!
$100 plus for two?? What do I search for that is the equivalent?

I still don't understand the numbers that attend this discussion.

I'll review and see if I can search for, say, 20W LED bulbs.? Is that what will work? Here I go.... guessing again :-)

Out of 6,130 forum members, you would have thought that someone might have fitted LED tail/brake light bulbs to their Hexhead.

In the UK, ABD were very helpful, perhaps AUXLIGHT or Sidaqi could offer some advice.

David. wrote: ↑Mon Jan 13, 2025 6:08 pm Out of 6,130 forum members, you would have thought that someone has fitted LED tail/brake light bulbs to their Hexhead.

Yes, I imagine someone has.
Did they all pay 100 British ponds plus?? for that??
I'll try searching "21W LED 1156 bulb" and see what shows up.

I'm stable now with 1 filament and one LED. Not happy with that, but as a famous British song writer once sang...
"You can't always get what you want!"

David. wrote: ↑Mon Jan 13, 2025 6:08 pm Out of 6,130 forum members, you would have thought that someone might have fitted LED tail/brake light bulbs to their Hexhead.

The problem is only a handful of those 6130 actually log on to the forum on a regular basis.

I found this.

https://www.amazon.com/gp/product/B09B2 ... Y1DMQ&th=1

If, IF, ....it really uses 21W, as it claims, then the resistance should be identical to a 21W filament bulb....???... I think.

Maybe W's are different between LED and filament? Who knows.

Sorry to say but you may be disappointed.

Copied from Amazon specs on the page I linked to...

"Light Source Type
LED
Wattage
21 watts"

I believe, in my post, I stressed If sufficiently.

Yes, I probably will be disappointed. I have been many times with this effort. It may be that $100 bulbs are the ONLY recourse.

At least Amazon returns are easy.