1978 R100/7 : all components within the charging system are new and functioning correctly, strong battery, brushes/springs in good order, clean rotor surfaces, no loose wires up in the Speedo/tach housing, etc. etc.
The problem: the red charging light will go on, albeit a slight flicker on again/off again with the bike running at 3000 plus RPM. Not at lower RPM, just the mid-upper end of the tachometer range.
The light goes on when the key is turned on, goes out once the bike is started, as it should.
Problem existed before and after installing a Katdash for the bike.
Any thoughts?
I’ve never really understood how that light works, so I really can’t help - but, the light should be on at idle speed, then gradually go out as rpm’s rise. I think it should be off by 14-1500rpm or so. I’ve seen mine glow dimly at higher rpm’s when riding in the dark. Rick Jones once told me that is not too unusual for an airhead. it’s a strange circuit with that bulb, kinda like it is “hanging in the balance” in some kind of series circuit.
I had a similar issue on my 75 R 90. I tried everything with no joy. One day I unplugged the signal flasher unit. Problem resolved. If I put the flasher back in the problem returned. Replaced the flaher unit with an automotive 3 prong one and all is well with the generator light.
Cheers!
John
The Alternator output warning lamp is 100% controlled by the Voltage Regulator. The OEM voltage regulator is an analog device composed of relays and contacts (like "ignition points") which open and close. No owner would expect a set of ignition "points" to be good after 50 years, but here we have the same setup inside the 50 year old VR. What could possibly go wrong?
Bosch themselves stopped make analog VRs about 1990, when they converted over to a solid-state VR that operates much better, and works by controlling things using transistorized circuits which have no moving parts. The Bosch design originally used on Airheads was also in common use on a lot of period automobiles (Saab, Volvo, Mercedes...), meaning you can still buy plug-compatible solid-state VRs very cheaply. And this is where I suggest you start.
Or, you can buy the equivalent device from Motorrad Elektrik for $39 from the bottom of...
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
The "charging light" is 100% controlled by the Voltage Regulator. The original equipment VR is comprised of relays and contacts that open and close to effect the correct battery charging. Now no one in their right mind would leave the original set of "ignition points" in their 50-year-old Airhead and expect it to run right, but the contacts in the OEM VR are the exact same thing... contacts that open and close.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
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