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Old 04-24-2013, 03:56 PM   #1
B_C_Ries OP
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Generator Light

I have a 1977 R100/7 and my generator light has been on since 1987 when I bought it.

It isn't bright but it never goes out, it gets dimmer as the RPM's increase up to about 4,000 then it gets a bit brighter after that.

I worried about it for a few months in the late 1980's even replaced the diode board because one corner looked a bit fried, then I just got used to it,

It does go out when I turn off the key.
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Old 04-24-2013, 05:20 PM   #2
disston
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So it sounds like it is charging the battery because you have had this problem for 15 years (is that right?). How may years, ruffly, do you get out of a battery?

I'm not one of the electrical experts but I'm thinking the brushes need to be checked. They are held in place by coiled springs and the springs have to be installed correctly. They can be put in with not enough tension. This may give symptoms like you report.

Other than that it is not a bad idea to clean all the terminals. There is a voltage regulator too, you know?

And BTW, it is an Alternator. That's why you have a diode board. A generator puts out DC Voltage.
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Old 04-24-2013, 06:54 PM   #3
B_C_Ries OP
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it reads 'Gen' right under the light,
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Old 04-24-2013, 10:18 PM   #4
Warin
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Basics -

the light will only glow if there is a difference in voltage across it.

the light is connected between the battery and alternator.

Extras

The lights' 'battery' connection goes through several connections - each one has some load on it and you will get a voltage drop along it. If those voltage drops get high enough you will have a glow on the 'gen' light. Measure the 'battery' voltage in the headlight shell and you will have some idea of this voltage drop.
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Old 04-24-2013, 11:54 PM   #5
disston
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Quote:
Originally Posted by B_C_Ries View Post
it reads 'Gen' right under the light,
You have a point. (This is where I jump up and down screaming, "Damn Krauts!" repeatedly.) So I wlll have to admit it is a "Gen" light. But only the light is "Gen". The thing that charges the battery is an Alternator.
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Old 04-25-2013, 04:29 AM   #6
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Upon reviving my airhead, the charging system worked ok - putting out ~14 volts but the charging light was dimly lit. Since that sort of thing drives me crazy, I set out to make the light go out. It turns out (in my case) the wires from the stator to the diode board were old/corroded and putting in new wires got the light to extinguish completely. I got new wires from euromotelectrics, but BMW still makes OEM replacements. YMMV.
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Old 04-25-2013, 07:24 AM   #7
Bill Harris
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Actually, Charlie, blame it on the 'Mericans and not the Krauts. In the '70's manufacturers had to start labeling all switches pa Angliski instead of using (reasonable) pictograms and the gummint prolly specified "GEN" light.

Agreed on the light being lit-- it shows a difference in voltage and suggests somthing amiss, probably in the headlight bucket connections. That "GEN" ;) light frequently shares power with the other waring lights (and other things), so pull out the schematic and start tracing. If that circuit does fail, it will do so during a cold dark thunderstormy night far from home...

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Old 04-25-2013, 08:08 AM   #8
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Quote:
Originally Posted by B_C_Ries View Post

I worried about it for a few months in the late 1980's even replaced the diode board because one corner looked a bit fried, then I just got used to it,

Why are you worrying about it now?

If you do want to rectify the situation, no pun, you'll have to start tracing circuits as suggested.

My guess is a bad ground...somewhere. When you replaced the diode board did you also replace the ground wire(s)?
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Old 04-25-2013, 09:45 AM   #9
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It is irritating, and I wondered if anybody else had similar issues
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Old 04-25-2013, 03:29 PM   #10
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I had the same issue for many years.

Dull glow at night. It did not worry me that much as the battery was charging, however it became annoying.

I tried many things to try and resolve however to no avail.

Start with the cheap fixes. As suggested previously, check and clean all connections.

Eventually I removed and cleaned the ignition switch with electrical contact cleaner. Now the light no longer glows.
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Old 04-25-2013, 03:41 PM   #11
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Quote:
Originally Posted by B_C_Ries View Post
It is irritating, and I wondered if anybody else had similar issues
You will have a lot of different solutions - all work for a particular situation. You could apply all the diffrent solutions offered and still have your fault.

YOU will not know what to do until you make MEASUREMENTS.
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