Evasive /7 Generator Light Problem

[BillB]

I have been chasing a problem with the generator light coming on periodically but with no apparent pattern or connection to immediate circumstances on a 1978 /7 R100 for over a year and a half and need some fresh ideas. During that time and one at a time, I have replaced the rotor, brushes holder, stator, diode board, voltage regulator, and main relay. After each step, the charging light comes back on intermittently, sometimes dimly and sluggishly, and sometimes brightly and insistently. While the connections do not have any apparent corrosion, I have tried to go through and clean them up. I suspect the problem is in the wiring or connections but could use some ideas on how isolate or identify the problem. I have tried to work through some of the testing sequences available on the internet but end up with the same problem after installing a new part. Does anyone have any suggestions or experience that might help?

[SteveD]

Wilkommen.

You seem to have covered most of the usual suspects. How frustrating.

New brushes with the brush holder? Are they wound on adequately?

Is it after the bike is hot? Something plays up when hot? From memory the Veg had something like that with his stator on a R100r.

The intermittent nature has me thinking something loose, cracked? But what? The 3 wires from alternator to diode board? Other than the diode board mounts, they're the only things you haven't mentioned. Maybe add another ground wire from the diode board and see if it helps. If so, solid mounts.

[BillB]

Usually it takes a while for the light to start coming on, and initially, it stays on only very briefly. But after the last time I went through the possibilities and added a new flasher unit to get the turn indicators working again, the charging light came on almost immediately and stayed on for extended periods. That had me make for home in a hurry as I did not want another long walk home with a dead bike.

I also suspect something cracked or loose but have yet find anything. I have replaced two or three of the major sections of the wiring and gone through variations on the mounts for the diode board several times only to come back to the same problem.

The brush holder came with new brushes. What do you mean by being wound adequately?

[Wobbly]

► I had intermittent low output issues until the new brushes seated in, which took about 500 miles.

► Additionally, at first glance, it looked as if the spring pressure on the brushes might be too strong, leading to accelerated brush wear. So I considered lowering the pressure until I saw it caused an interference. Did you replace the springs just like they came out ?

► In helping a person on another forum, he realized a mechanic had grafted 2 harness halves together during a complete front end replacement, rather than unplug the main harness from the headlamp and gauges. Mechanics are notoriously BAD at doing electrical repairs correctly. You don't see any signs of harness tampering, like lots of electrical tape wound around, do you ?

Wishing you luck !

[SteveD]

The brush holder came with new brushes. What do you mean by being wound adequately?

Refer to spring pressure as mentioned by the wobbler.

[BillB]

The brushes not being properly seated and the spring pressure not being right make sense to me for when the generator light is dimly lit, and I’ll take another look at them, but could they also be related to the erratic and increasingly prolonged shifts to the light being on at full intensity?

[SteveD]

A bit of GEN light Boxerworks history here...http://forum.boxerworks.com/viewtopic.p ... =GEN+light

[ME 109]

What does a multimeter on the battery say about the light variations?
Could it be a short to the charge light somewhere in the instrument pod?

[BillB]

The suggestions about the springs on the brushes were helpful, but the problem remains. One of the springs for the brushes was a full rotation looser than the other one and the ones on the old holder, but once I had corrected that and started up the bike, the generator light came on at full intensity within minutes and, if anything, stayed on for longer periods once the bike was warmed up. The brushes look like they have a good start on being properly seated. Thank you for the link to the general discussion. I will work my way through it. The light just seems to come one while I am riding, but I will see if I can get it to do so while I have a meter on it. The possibility of a short in the instrument pod seems promising. All the connections and wires look good there. Is there some way I could chase it down with a test light?

[Gibson]

I have been having a similar problem with my r100r. I get intermittent light also. When the voltage is low, signal lights will self cancel. I have a glass matt sealed battery. I think it could have to do with the battery in my case. An internal short may be causing drop in voltage. It is very random.