Vintage BMW Motorcycle Owners

Ok, here's the situation ...

I installed some "dual filament" LED lights to my Enduro bags and tied it into the lines that run to the brake light, which also has LED upgrade.

When the headlight is not on, everything functions perfectly.

When the headlight is on, all the lights in the shell dim and the Enduro bag lights do not come on nor the brake light ie in running light mode. Even with the brake pedal depressed, the main brake light is much dimmer and the Enduro bag lights not at all.

Occasionally, when I turn on the headlight, the shell lights do not dim and all the lights work perfectly! The Enduro bag lights and brake light come on as running lights and when the brake pedal is on they all increase in brightness. But, after a few brake pedal actuations, it goes back to the bad way.

Some sort of short in the wiring harness due to decaying insulation? Would be a nightmare to trace. I made sure the ground to the engine block is clean and secure. Removing the headlight makes no difference so not a current drain situation.


H E L P!

Assuming you have the stock 6v system... Is your charging system working properly? Do you have over say 6.6v at the battery when the engine is revving? What is the state of your battery? Are the LEDs of the 6v variety?

I am using the stock system, its charging well and I just installed a 18Ah gel battery, the LEDs are indeed rated for 6VDC.

Anybody out there with ideas before I have to replace the entire harness? Oh I also liberally sprayed the contacts of the key switch with contact cleaner in case there was poor contact in the rotary switch.

If it were me, I would attempt to get the bike back to a condition before the LEDs were installed and see if the power fluctuations were gone. If so, then begin adding the LEDs back in and see when/if the problem reappears. It sound's like there's some corrosion somewhere which is minimizing the current allowed through the system. It could be that your electrical system is marginal without the LEDs and you didn't really know that. Now with the LEDs, you've pushed the system over the edge and its weakness is now visible.

Most DC electrical problems are ground related. You might want to start there.

This may, or may not, be of help to you, but a few comments...

Your LED tail light upgrade may already have "blocking diodes" on the ckt board to prevent feedback to ground, (some do, some don't), but these MAY needed in order to run additional tail/brake saddle bag lights in parallel with the coffee can LED conversion. The LED conversion I purchased from Benchmark works did not have blocking diodes on the ckt board. After consulting with the manufacturer, I had to install diodes in order to block the current path to ground. When a path to ground occurs, you will get weak or no lights under varrying circumstances. I understand a design change has since been initiated to incorporate blocking diodes on the LED board.

You may have to either install blocking diodes in series with the coffee can LED board, (if it has none); or install blocking diodes in series with the LED lights in the saddle bags.

In my case - I had installed filament bulbs (not LED) to act as brake lights in parallel with the LED brake light. What was funny was the brake lights worked just fine, but the the regular LED tail lights would not light at all. And the license plate LEDs burned at "half brilliance" until I stepped on the brake, and then they worked fine. What was happening was the current was going through the filament saddlebag lights to ground, instead of the tail light resistors and the LEDs, but not lighting up either the coffee can LEDs (tail), or the brake light bulbs in the saddle bags.

As I said, this may have nothing to do with your particular problem, but BIG TIP: I had no problems until I installed the saddle bag lights.

Bottom line suggestion: Contact the coffee can LED conversion manufacturer and he will/should help you out with what you need to do.

good luck,
fred

Fred,

Your message steered me into the right direction and a solution. It was the LED brakelight unit. Somehow it was shorting to ground, maybe the clips holding the reflector and lens in place had pierced the rubber gasket and allow current to exit via the chrome bezel. Once I removed the unit and let it just sit free by itself everything worked correctly and without failure!!

Thanks to all for helping to solve my dilemma.


Jim