84 R100 Not Charging - No GEN Light

[m_stock10506]

My 1984 R100 stopped charging last weekend. I made it home with 10.25 volts on the battery (only a year or so old). Battery recharged okay and holds the charge. The GEN light is not on when I turn the ignition On.

I pulled the voltage regulator and grounded the blue wire and the GEN light lit up, so I know the bulb and the instrument cluster wiring is okay.

Next, I took off the front cover (disconnect the battery first) and examined the alternator. Took off the stator, tested the rotor - there is no continuity between the slip rings. This indicates an "open" in the rotor. So I ordered a new rotor from EME. The new rotor tests at 2.9 Ohms between the slip rings. I mounted the new rotor and reinstalled the stator. The GEN light still won't light up - not charging.

Is the only other possible issue the brushes? Or, is there something else to check?

 

[pglaves]

The circuit is battery to ignition switch to kill switch to light bulb to regulator to hot brush, through rotor, to ground brush to ground.

9 times out of ten it is an open rotor. Or occasionally worn brushes.

bet on a bad rotor.

 

[m_stock10506]

Paul - I tested the original rotor and it showed no continuity, an open in the rotor. So I replaced it. That's why I posed my original question. After putting in a new rotor (2.9 ohm resistance between the slip rings), the GEN light still isn't lighting. I appreciate the electrical path you provided in your reply. I will try to follow that to see if I can determine where the remaining fault is. So, other than a bad rotor, the brushes are the only other source?

 

[guenner]

Try the "blue wire test" again just to make sure your GEN light works.

/Guenther

 

[lkchris]

Simple.

If the light bulb for the GEN light is burned out, the charging system will not charge the battery.

 

[typ181r90]

Simple.

If the light bulb for the GEN light is burned out, the charging system will not charge the battery.

from first post

"I pulled the voltage regulator and grounded the blue wire and the GEN light lit up, so I know the bulb and the instrument cluster wiring is okay."

 

[guenner]

typ181r90: Yeah, that was BEFORE he worked on the charging system.

lkchris: Not that simple! The current through the GEN-light bulb (~025A) is needed to "kickstart" the alternator. If the alternator was recently used there is still enough magnetism left to produce enough amps to get the charging (and voltage build-up) going without the "kickstart" current.

/Guenther

 

[m_stock10506]

Try the "blue wire test" again just to make sure your GEN light works.

/Guenther

I have opened up the front engine cover again to start tracing the circuit and try to find the problem. First thing I tested (again) was the GEN light circuit. Blue wire at the VR gets grounded and the GEN light still works.

Following the path that was given earlier, am I testing this path for continuity? Since I know that the GEN light works from the voltage regulator, then am I now testing continuity from the VR to Hot Brush to Rotor to ground brush?

I can visually confirm brushes are coming down the brush holder and making contact with the slip rings.

I'll report back once I try to check this circuit path. Not sure how quickly I'll get to it.

 

[guenner]

One test of the GEN-light path is to jump the slip rings with a short piece of wire:

View attachment 46592

If the GEN-light comes on you have connection from the light bulb all the way through the brushes to ground.

/Guenther

 

[20774]

One test of the GEN-light path is to jump the slip rings with a short piece of wire:

Be sure the brushes are lifted off the slip rings...a business card slipped under them works fine.

 

[guenner]

Kurt,

you only need to isolate the slip rings with some paper/plastic if you want to measure the resistance of the rotor.

My suggestion was to bypass the rotor coils with a jumper and test the wiring from the light bulb through the brushes (and the jumper wire) to ground.

/Guenther

 

[20774]

you only need to isolate the slip rings with some paper/plastic if you want to measure the resistance of the rotor.

My suggestion was to bypass the rotor coils with a jumper and test the wiring from the light bulb through the brushes (and the jumper wire) to ground.

Got it...you weren't measuring resistance...you were creating the path to ground to check the light!

 

[beemerguru]

How much life left on the brushes?

New rotor didn't work,,,we know the bulb is good, you know the wiring is good, have you checked the stator or tried swapping out VR? Not much left to check except diode board.

 

[Jameslf1]

alternator no charge lite

As pointed out,the lite path is thru the regulator,thru the rotor to ground. As the current in the rotor builds feedback thru the 3 small positive diodes at d+ returns back thru the regulator thru the rotor to ground increasing output. At 2.9 ohms & 12.4volts you have 4.2 amps rotor draw,more or less. Unplug terminal at d- and ground the male spade to metal case,key on,engine off (not running). The lite should go on & off as u make and break the male spade circuit. If not go back to Df and repeat the procedure. If no lite go to your blue wire at D+ and check ,if lite is on & makes & breaks w grounding ,the problem is between the D+ and Df ie the regulator.To verify use jumper wire from Df to D+,remember key on, engine OFF. The lite should be on and go on/off as you make/break the circuit.
The stator can be checked by just unplugging the 3 wire connector & check the male spades for continuity and to ground. Stator resistance is too low to have much meaning except continuity. Charging can be checked at B+ w a voltmeter w engine running once gen lite problem is corrected. Hope this helps.

 

[FChatfield]

82 R100RS Not Charging - No GEN Light

My 1984 R100 stopped charging last weekend. I made it home with 10.25 volts on the battery (only a year or so old). Battery recharged okay and holds the charge. The GEN light is not on when I turn the ignition On.

I pulled the voltage regulator and grounded the blue wire and the GEN light lit up, so I know the bulb and the instrument cluster wiring is okay.

Next, I took off the front cover (disconnect the battery first) and examined the alternator. Took off the stator, tested the rotor - there is no continuity between the slip rings. This indicates an "open" in the rotor. So I ordered a new rotor from EME. The new rotor tests at 2.9 Ohms between the slip rings. I mounted the new rotor and reinstalled the stator. The GEN light still won't light up - not charging.

Is the only other possible issue the brushes? Or, is there something else to check?

Michael, I came across the thread you started in 2014 when you were having the same situation I am now: Motorcycle not charging, no GEN light. I'm curious to learn what resolved your problem.

Frederick Chatfield
Richmond, IN
1982 R100RS

 

[robsryder]

I believe that the solution to the 2014 charging issue was worn brushes. Rick Jones of Motorrad ELektrik is a good source for parts. Rick began using crimped on "eye" type connectors thus avoiding the need for soldering. I believe this was the solution for Micheal Stock's bike.

 

[Omega Man]

Pretty cool the members still connect on an old thread
OM

 

[m_stock10506]

Michael, I came across the thread you started in 2014 when you were having the same situation I am now: Motorcycle not charging, no GEN light. I'm curious to learn what resolved your problem.

Frederick Chatfield
Richmond, IN
1982 R100RS

I'm somewhat embarrassed to see that I never posted a "final update" to this post. That is something that I try to do on any post that I originate, so that it has a final conclusion. Looking through my maintenance log, I see that this problem and its fixes got muddied up and there wasn't a clear solution to this, which may be why I never posted an ending.

I can't swear to every step that was taken (over six years ago), but it appears, that I ordered a new rotor to replace the rotor that clearly had developed an open circuit. In addition, I ordered new brushes to replace worn brushes. At the time, I wasn't aware of the replacements available from Motorad Elektrik with eyelets on their ends, so those brushes had to be soldered into place. The problem still existed. I examined the rotor and stator and saw scratches. Removed the parts and the rotor had made contact with the inside wall of the stator. I apparently did not get the stator reinstalled completely square. I don't know if that was the only issue, or if the diode board had also failed when the rotor failed, or when the new rotor scratched the stator.

Faced with all these parts that had to be replaced, I opted to order a new replacement kit. I ended up installing the Enduralast II alternator kit from EME. The kit cost was close to just my cost of replacing my damaged parts, and included all new parts. So, new diode board, rotor, and stator installed. Kit had a slightly higher output than the OEM setup, but the pieces were all similar to OEM, so function was still the same.

Looking through my maintenance log today, the EDL II kit has been installed for over 6 years, 4 months, 38,500 miles. The only work done at the alternator was a front brush replaced. Replaced brush was a Motorad Elektrik brush with eyelet, so replacement was just break off the old brush wire, undo the nut at the brush connection and slip the eyelet onto the connector.

Bottom line, for you Frederick, I can't point to one item that was wrong with mine. If you aren't getting a GEN light, first verify the GEN light works. Then test the rotor for an open. Then verify that the brushes are making contact. Then pull the diode board and test it. There are several excellent trouble shooting write ups from folks with way more experience than me.

 

[20774]

Here's Snowbum's "all inclusive" and detailed web page on troubleshooting the charging system:

https://bmwmotorcycletech.info/trbleshootALT.htm

 

[stevenrankin]

After

I can relate to troubleshooting a problem for a long time only to never find a smoking gun. I chased a cut out of my entire electrical system which started with a skip in the ignition and ended up with the bike completely dead at the side of the road.

After two years of messing around, the problem is solved. What did I find to cause it? Who knows, I never did one thing I could point at to solve the problem. Best guess is I had a bad ground somewhere.

That gremlin is off on another bike somewhere and I hope he never comes back. St.