Boxerworks.com

So the broken wire wasn't the entire fix. It did help the red light go off (it was faint at higher revs).

The charged battery puts out 13.2V with the bike off.
The battery terminals measure 13.2 with the bike at idle and
The battery measures 13.8V with the bike at a high RPM
It has a Wherle voltage regulator which should put out 14.2. I've swapped with a known working voltage regulator and i have the same results.
Brushes are OK. diode board tests OK.
The only thing that is suspect is the Rotor... I'm ordering a new one today. If that doesn't solve it, I am going to smash my head into a wall.

13.8v at high RPM...and you think there's a problem? I'd pack up and consider it solved. You're probably not getting 14+v because of poor connections or corrosion somewhere...possibly inside your heavy cables which most don't really see. 13.8v is not bad, all things considered.

Kurt in S.A.

Kurt in S.A. wrote:13.8v at high RPM...and you think there's a problem? I'd pack up and consider it solved. You're probably not getting 14+v because of poor connections or corrosion somewhere...possibly inside your heavy cables which most don't really see. 13.8v is not bad, all things considered.

Kurt in S.A.

+1

!f you're getting, say, 12.6 or 12.7 volts, measured at the battery posts, with your maximum load on (lights, running lights, etc.) You're good to go. That doesn't mean your charging can't be improved with newer wiring (such as battery cables mentioned) along with making sure pertinent electrical connections are clean (low resistance) and so forth.

Now if you're trying to run a heavy load (such as running lights and a heated vest) you're approaching needing expensive aftermarket equipment.

Generally speaking, I wouldn't expect a rotor to degrade in performance. I would expect it to fail, and when that happens you know you have a problem. There aren't a lot of discrete windings and electrical connections inside a rotor, like a DC generator will have. There is one winding which interfraces with the electrical system through the two slip rings. You might make sure that your slip rings are bright and that you have plenty of brush pressure (more than you might think is needed). If that is all in order that's about as good as you can do.

Nor will a "heavy duty" or similar such voltage regulator help. If your charging system doesn't have it, a heavy duty voltage regulater won't put it there.

Perhaps some food for thought.

Addendum: I would recommend buying a spare rotor though. They do fail and having one handy can and does come in handy (sorry).

Ken

Kurt in S.A. wrote:

jjwithers wrote:I'm 90% sure /5 had a different diode board.

Different in what way? IIRC there were two manufacturers, Bosch and Wehrle. Some had bent-over diodes and some didn't (Wehrle). Later versions had an extra set of smaller diodes. But in general, they were the same type of unit. Now if you want to discuss Thunderchild...they were strictly aftermarket. Then there was some kind of Guzzi-style board.

Kurt in S.A.

The 180W alt is 3 phase, three wires running from the fields to the diode board. The /6 and later 240 and 280W units are four phase, and have four wires running from the fields to the diodes.

That being said, the later 4 phase diode board can be used on a 180W alternator using only 3 sets of diodes, and works fine. Likewise as 3 phase diode board can be used on a 280W alternator but you will only get 180ish watts of output. I don't know how long the 3 phase diodes will last on a later application.

Garnet wrote:The 180W alt is 3 phase, three wires running from the fields to the diode board. The /6 and later 240 and 280W units are four phase, and have four wires running from the fields to the diodes.

That being said, the later 4 phase diode board can be used on a 180W alternator using only 3 sets of diodes, and works fine. Likewise as 3 phase diode board can be used on a 280W alternator but you will only get 180ish watts of output. I don't know how long the 3 phase diodes will last on a later application.

Garnet, I'm afraid you're mistaken about the later alternators being 4 phase. If you look at a diode board you will see only 6 high current diodes plus a few low current diodes. The 6 diodes are what is required for a full waye three phase bridge rectifier.

Rob Frankham has a wonderful write up on testing a diode board and in that write up he gives a schematic diagram of the board, which shows only 3 phases.

Unfortunately a quick search didn't reveal his writeup. Perhaps someone will have the link.

The fourth wire you're likely looking at will be the neutral wire leading to the neutaral in the "wye" connected field coils.

Editing: What I did find is a pic of the diode board on Stephen Bottcher's (a sometime boxerworks contributer) site. The pic shows the 6 high current diodes I'm talking about.

Ken

Ken in Oklahoma wrote:

Garnet wrote:The 180W alt is 3 phase, three wires running from the fields to the diode board. The /6 and later 240 and 280W units are four phase, and have four wires running from the fields to the diodes.

That being said, the later 4 phase diode board can be used on a 180W alternator using only 3 sets of diodes, and works fine. Likewise as 3 phase diode board can be used on a 280W alternator but you will only get 180ish watts of output. I don't know how long the 3 phase diodes will last on a later application.

Garnet, I'm afraid you're mistaken about the later alternators being 4 phase. If you look at a diode board you will see only 6 high current diodes plus a few low current diodes. The 6 diodes are what is required for a full waye three phase bridge rectifier.

Ken

I'm outa phase again?

What phase of the moon are we in?

Rob's page: http://robfrankham.co.uk/bike/bike_index.htm

Stephen's page: http://www.stephenbottcher.net/BMW/misc ... System.jpg and

http://www.stephenbottcher.net/BMW/diodeboard.htm

Kurt in S.A.

Kurt in S.A. wrote:Rob's page: http://robfrankham.co.uk/bike/bike_index.htm

Hmmm, Rob's link won't play on my computer. Can anybody else get it?

I would hate if if Rob's stuff is no longer available.


Ken

Kurt in S.A. wrote:13.8v at high RPM...and you think there's a problem? I'd pack up and consider it solved. You're probably not getting 14+v because of poor connections or corrosion somewhere...possibly inside your heavy cables which most don't really see. 13.8v is not bad, all things considered.

Kurt in S.A.

You are correct. The more I think about it, The more i wonder if the battery is the culprit. It is a shorai battery and I can charge it through the accessory charger plug but maybe it isn't charging across the terminals.
The /5 electrical system is so simple but when something isn't doing its job, it causes lots of head scratching in the garage...

Garnet wrote:I'm outa phase again?

What phase of the moon are we in?

Don't worry about it. It's just a phase...