Finally some nice weather so I decide to ride the 1983 R100RS down to St Louis to see my son. About an hour from home, the volt meter drops to just a hair under 12 and the red generator light starts to glow faintly. Normally the volt meter points to between 13 and 14 when cruising at highway speeds and, of cours, no red light. I need gas so I stop, fill the tank and have a short pit stop. When I restart the bike, volt meter goes back to between 13 and 14 and the red light goes out. Stays this way for the remainder of the trip (two more hours). The bike has 63,000 miles on it and had a new battery in April 2016. When not in use the bike is always on a Battery Tender. Pretty sure the bike is sending me a message here and since I want to take the bike on a trip this summer (1000 miles round trip) would appreciate hearing any ideas about what is going on.
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Charging Issue?
- Thread starter 217don
- Start date
stevenrankin
Active member
Possible solution
It is possible that one of the brushes on the alternator hung up or was not making contact for a bit. I had this happen after the bike sat for the winter.
When was the last time the brushes were checked? They could be worn out or the springs could have lost their spring.
Of course, there could be a whole lot of things going on from a dirty contact/connection to a major failure. Problems that show up and then go away are such a pain to track and fix.
Good luck. St.
It is possible that one of the brushes on the alternator hung up or was not making contact for a bit. I had this happen after the bike sat for the winter.
When was the last time the brushes were checked? They could be worn out or the springs could have lost their spring.
Of course, there could be a whole lot of things going on from a dirty contact/connection to a major failure. Problems that show up and then go away are such a pain to track and fix.
Good luck. St.
happy wanderer
Day Dreaming ...
Ohhhh this sound soooo familiar! The last time I had this behaviour I diagnosed the problem to be the diode board. Replacing it fixed my issue but I got curious and examined the bad diode board with a magnifying glass. What I found was that one solder joint on one of the big diodes had come loose and the diode lead was floating in the hole. It was very hard to notice at a glance. I just put a lot of solder flux on the joint after cleaning it up with a brass brush on a dremel tool and re soldered it with some good acid core solder.
Put it back in and the bike ran fine for a few more years. I have carried the new one as a spare on whichever airhead I am traveling on ever since. And we all know if you carry a spare that part NEVER breaks down on the road!
What happens is heat makes the metal solder joint expand and it loses contact. Then it cools down again and sort of makes contact again which is very frustrating to trouble shoot! I think the newer diode boards with that covering on the back are not as susceptible to this as the old ones were.
Put it back in and the bike ran fine for a few more years. I have carried the new one as a spare on whichever airhead I am traveling on ever since. And we all know if you carry a spare that part NEVER breaks down on the road!
What happens is heat makes the metal solder joint expand and it loses contact. Then it cools down again and sort of makes contact again which is very frustrating to trouble shoot! I think the newer diode boards with that covering on the back are not as susceptible to this as the old ones were.
m_stock10506
Well-known member
217Don - I hope you realize that without symptoms now, it could be anything in the charging system. Both of the above possibilities are each good chances. At 63K miles, worn brushes are a good and cheap possible. Take a look at the site for Motorrad Elektrik. They sell replacement brushes with a ring terminal on the end. It makes it SO EASY to replace the brush. No soldering, just remove the screw and slip the ring on and tighten it back up.
http://www.motoelekt.com/charging.htm
http://www.motoelekt.com/charging.htm
pglaves
#13338
If all this bike is used for is very local riding it would be OK to wait till the defect becomes more prevalent and easier to diagnose. However if the bike is ridden beyond battery depletion range - say 100 miles - from home then I would take a more preventative approach. By that I mean a close physical examination of the system. Check the rotor for crud on the slip rings. Carefully examine the diode board, even with a magnifying glass looking for solder defects and any sign of blackening or heat. Check all of the connections for grime, looseness, or corrosion. Check the rotor for proper continuity cold and after being warmed with a hair dryer.
If that provides no apparent remedy than I would at a minimum carry a spare diode board and spare voltage regulator.
If that provides no apparent remedy than I would at a minimum carry a spare diode board and spare voltage regulator.
Thanks for the suggestions. Since I made it to St Louis, I had it checked out by the BMW dealer there. They said brushes and ground were good and could not find anything wrong with the charging system. Hot or cold it seemed to crank out 14 volts. I really would like to take it on a trip this summer up the Great River River Road.
Any pictures of the slip rings and/or instructions on how to remove and replace the diode board? Also what to look for when examining the diode board? It has been replaced with an aftermarket board some years ago that was described as a superior to stock unit. I don’t have access to my service records just now so I can’t check exactly when the board was replaced.
Any chance you could open the front cover (remove the battery ground) and take a picture of the diode board? We could tell which kind you have.
Removal isn't that big of a deal. It starts by taking pictures of all the wires and connectors. Then begin removing the wires you can see. Likely there will be four nuts at the corners which will need to be removed. Once the board is free, it will still have wires connected to the backside. Try and get pictures of those wires/connections before you remove them.
Not sure you'll be able to see much that's wrong unless there are some serious burn marks, etc. Usually it takes some serious testing to check out the diode board. Lengthy article by Snowbum on troubleshooting the charging system:
http://bmwmotorcycletech.info/trbleshootALT.htm
If the diode board was something that came from Rick at Motorrad Elektrik, he would be a good guy to call:
http://www.motoelekt.com/charging.htm
Removal isn't that big of a deal. It starts by taking pictures of all the wires and connectors. Then begin removing the wires you can see. Likely there will be four nuts at the corners which will need to be removed. Once the board is free, it will still have wires connected to the backside. Try and get pictures of those wires/connections before you remove them.
Not sure you'll be able to see much that's wrong unless there are some serious burn marks, etc. Usually it takes some serious testing to check out the diode board. Lengthy article by Snowbum on troubleshooting the charging system:
http://bmwmotorcycletech.info/trbleshootALT.htm
If the diode board was something that came from Rick at Motorrad Elektrik, he would be a good guy to call:
http://www.motoelekt.com/charging.htm
RPGR90s
Member
Charging
Just a guess but are you running a mechanical voltage regulator? Can't remember if they switched to electronic in '83.
Just a guess but are you running a mechanical voltage regulator? Can't remember if they switched to electronic in '83.
I don't know what sort of voltage regulator it has. I could look - where does it live?
I picked the bike up at Gateway BMW yesterday and rode it home (189 miles) in slightly under three hours. No issues whatsoever with the charging system. Voltmeter read between 13 and 14 the whole time and GEN light was off except at idle.
Gateway said the brushes looked good and they had checked the continuity. (I have to confess I don't excactly know what continuity means in this context.)
stevenrankin
Active member
Fyi
Gateway said the brushes looked good and they had checked the continuity. (I have to confess I don't excactly know what continuity means in this context.)
I assume it means a check of current flow from one brush though the rotor and out the other brush. Looking for a complete circuit through these components.
A continuity checker will beep if there is a complete circuit from brush to brush as there should be. No beep and there could be a brush not making contact or poor contact. It would also mean a bad rotor.
Does this help? St.
Gateway said the brushes looked good and they had checked the continuity. (I have to confess I don't excactly know what continuity means in this context.)
I assume it means a check of current flow from one brush though the rotor and out the other brush. Looking for a complete circuit through these components.
A continuity checker will beep if there is a complete circuit from brush to brush as there should be. No beep and there could be a brush not making contact or poor contact. It would also mean a bad rotor.
Does this help? St.
eurotourer
New member
I had the same intermittent charging problem on my R75/5 and also a friend on his R100RS. In both cases it turned out to be the rotor. Fortunately at that time just the rotor was available. Good luck.
RPGR90s
Member
Vr
The Voltage regulator is mounted to the right side of the frame under the tank on my /6. Not sure if it's in the same place on a '83. In any case it should have a three terminal plug on the bottom. Mechanical voltage regulators are metal, electronic are plastic housing and usually maybe an inch or so tall.
Continuity refers to a circuit being complete (very low resistance). In the case of the alternator, rotor and brush assy., you want continuity between one brush terminal to the other as that ensures the path is complete between the brush, through the slip rings (front and rear) on the rotor and through the other brush.
The Voltage regulator is mounted to the right side of the frame under the tank on my /6. Not sure if it's in the same place on a '83. In any case it should have a three terminal plug on the bottom. Mechanical voltage regulators are metal, electronic are plastic housing and usually maybe an inch or so tall.
Continuity refers to a circuit being complete (very low resistance). In the case of the alternator, rotor and brush assy., you want continuity between one brush terminal to the other as that ensures the path is complete between the brush, through the slip rings (front and rear) on the rotor and through the other brush.
If you have the original, it would be something like in these pictures:
https://picclick.com/BMW-Voltage-Regulator-R50-R60-R75-R80-R90-220908678642.html
It's located under the tank, on the right side of the frame backbone.
Ok. I'll have a look as soon as I can.
Yes.
Was that from Motorrad Elektrik? He has the board for sale near the bottom of this page:
http://www.motoelekt.com/charging.htm
It's certainly been a while, but if you got it there, Rick could offer some guidance.
Looks pretty original. There are a number of aftermarket regulators that will work. Places like Motorrad Elektrik and EuroMoto Electrics will have a replacement. You can also look for Airhead substitutes on this page:
https://ibmwr.org/index.php/bmw-parts-substitutes/
I bought a Transpo unit IB301 years ago. I now carry the original on the bike for emergencies. Snowbum has tests to determine if the voltage regulator is bad. However, your problem seems to be intermittent and those are a bear to find.
https://ibmwr.org/index.php/bmw-parts-substitutes/
I bought a Transpo unit IB301 years ago. I now carry the original on the bike for emergencies. Snowbum has tests to determine if the voltage regulator is bad. However, your problem seems to be intermittent and those are a bear to find.
