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Old 05-21-2010, 10:14 AM   #16
Chihuahua Wrangler
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Joined: Apr 2010
Location: Tucson, AZ
Oddometer: 704
Gen Light Question...

This is slightly related to this topic, so I'm going to ask here instead of starting a new thread. History: My r65 had the speedo/tach removed by the previous owner (my father in law who passed away in November). He didn't replace the speedo at all, and wired in some sort of other-bmw model "dashboard" (see pic).

Yes, that is gum stuck to the high-beam light. My FIL was a character, for sure.

Now, despite how it looks, everything does work, and the system charges, etc. But I am planning on installing a TrailTech Vapor (with idiot lights) or an Acewell gauge that has all included... speedo, tach and idiot lights.

Here's the question: If the Vapor and/or Acewell lights are LED's, which I believe they are, will they allow the charging system to work? I read somewhere (maybe here) that an LED won't allow the charging system to work like it should, and I need to use a filament-type bulb.

Anyone know an answer to this? If it's true, I'll have to fabricate some sort of separate light just for the charging idiot light.
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Old 05-21-2010, 11:57 AM   #17
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Joined: Jul 2005
Location: Halfway between Munich and Redditch.
Oddometer: 1,980
Based on what the final resolution of the original question turned out to be, I'd say you do need a filament bulb in there.
LED lights do not behave the same in a circuit as filament lights do. This is why you have to add resistors to a system when you install LED turn signals. The lack of resistance makes them flicker instead of flash on and off.
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Old 05-21-2010, 01:09 PM   #18
What could go wrong?
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Joined: Mar 2007
Location: Beautiful Revelstoke BC
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Ron, usually I do all my own work.... BUT... if I ever have to take my BMW to a shop I hope you are the guy working on my bike, nice show of integrity.
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Old 05-22-2010, 03:03 PM   #19
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Joined: Feb 2005
Location: Paradise, TX
Oddometer: 681
Remember the way the system works is that the alternator spinning up offsets the 12v coming from the charge light and thus turns the charge light off. Without some load on that wire you have a short. So as least put a resistor on the line or better yet a bulb. The bulb actually tells you everything you need to know about the charging systems health.

And yes, an alternator will spin up a charge if it has enough residual magnetism in the rotor. I had a bad instrument board that prevented the charge light from lighting but kept the battery up for several days and thousands of miles.

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Old 05-23-2010, 12:39 PM   #20
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Joined: May 2009
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I simply added a small LED unit in the headlamp shell when I installed this Acewell good. The Acewell wiring does not fit the criteria for the BMW charging system.


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