LED upgrade for all bulbs

[David.]

https://www.autobulbsdirect.co.uk/blog/ ... king%20for.

"One of the core selling points of an LED bulb is the lower power draw."

LED 3W vs Filament 21W

[Strat Tuner]

SOLVED (I'm 80% confident)

Four 10W resistors arrived today, so I thought... lets try that....

My stable config was 1 filament and one LED.

I wired in one 10W resistor to the Filament bulb mount.
(the bulb and the resistor shared the GROUND/HOT wires. The resistor was as close to the bulb on the line as possible.

I replaced the filament with an LED and "Hay Presto" (Britishism), it worked.

Both LED bulbs have low power running voltage and Higher power BRAKE light voltage, and the CanBus god seems happy.

I won't know for certain until I've ridden it around town for a day or two, as I notice that CanBus errors can happen on the road even when there were none in the garage!

I'm not sure I understand WHY this worked... but that doesn't matter.

[Strat Tuner]

https://www.autobulbsdirect.co.uk/blog/ ... king%20for.

"One of the core selling points of an LED bulb is the lower power draw."

LED 3W vs Filament 21W

Well... yes. I do admire the lower power draw, but to what end?
Your BMW is banging out 12 volts constantly (from the battery and the generator), and it's not like you get to "keep" the power you save.

It's nice that it uses less power, but wow... it creates another big problem in resistance...

Consider what the world would be like if LED bulbs with THE IDENTICAL resistance were readily available for older machines. Stupid people like me wouldn't spend as much money trying to find something that worked...

(hmmmmmmmm.... perhaps I have my answer there?) :-)

[Strat Tuner]

now all that remains are those two cute little running lights on the front end above the lights.... probably not worth doing until the filament bulbs already in there go out.

[David.]

I'm not sure I understand why this worked.

Could this be the reason why.

I wired in one 10W resistor to the Filament bulb mount.
The bulb and the resistor shared the GROUND/HOT wires.
The resistor was as close to the bulb on the line as possible.

The resistor has been wired in parallel with the bulb.

What wattage is the LED bulb fitted.

[David.]

I do admire the lower power draw, but to what end.

Less power draw = less fuel consumption.

"One of the core selling points of an LED bulb is the lower power draw. Who doesn’t want an extra bit of fuel saving!"

[Strat Tuner]

Less power draw = less fuel consumption.

"One of the core selling points of an LED bulb is the lower power draw. Who doesn’t want an extra bit of fuel saving!"

I will take your word on that.

I'll attempt to find out what the watts are for the bulb that has the resistor.
Thank you for keeping this dialogue going!

[David.]

I'll attempt to find out what the watts are for the bulb that has the resistor.

Can the resistance (ohms) of the two LED bulbs fitted be measured with a meter. Then, at 12v, the power (watts) can be calculated.

[Strat Tuner]

I got one of those power measure resistance units this week... haven't laid hands on one in a decade, so will take so me time to figure that out...

[Strat Tuner]

SOLVED (I'm 80% confident)

Four 10W resistors arrived today, so I thought... lets try that....

My stable config was 1 filament and one LED.

I wired in one 10W resistor to the Filament bulb mount.
(the bulb and the resistor shared the GROUND/HOT wires. The resistor was as close to the bulb on the line as possible.

I replaced the filament with an LED and "Hay Presto" (Britishism), it worked.

Well... it worked in the garage! The first eight-mile ride around the town produced Yellow caution light errors! The worst was sitting at a long light with the brake on.

Now what do I do?

I decided since introducing the 10W resistor produced the best result so far, I'd go ahead and add the same resistor to the other bulb.
That worked in the garage, and a short test ride confirmed stability. I can now put two LED bulbs in as brake lights and CanBus is happy... even when the LEDs are NOT "Canbus friendly".

I put in the two brightest, best looking, red LEDs and went on an 80-mile tour of the California coast. This included heavy, stop and go, Freeway speeds up to 80 MPH, and tourists speeds for the beaches!

The yellow caution light didn't come on at all, EVER!

I think we're done here... at last....
thank you all for sticking with this exploration.

[David.]

Excellent, thank you for the feedback. When advice is asked for and offered in return, IMO, it is good to conclude and post with a positive result.

That way, others can benefit from the information provided.

Please have you got any photos of the final successful set up and/or links to the resistors and LED bulbs used, thank you.

[Strat Tuner]

Here's a photo...

Ah, the joys of bmw shaft drives!!

20250118_123325.jpg (266.56 KiB) Viewed 481 times

A sudden huge rattling made me pull over. Smoke from the shaftdrive greeted me.

I had hoped it would last a little longer than a month.
Bought it used with 112,000 miles on it.
Caveat emptor!