The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: MikeFossl on July 23, 2018, 07:20:38 PM
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Occasionally the light stays on after starting when cold. It usually winks out after a minute or two but it seems to be staying on longer and happening more often. Where should I start looking for a cause?
Brushes? Bad ground? Bueller?
Thanks!
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There are a whole mess of things it might be, so I'll throw in some assumptions followed by my 2c worth.
If the light is staying on strongly after startup my first port of call would be the brushes, check to see if they are worn down, and if not worn down, whether or not they are sticking. That white plastic gets terribly fragile with age and as a BMW part it will make your eyes water. The good news is that as far as Bosch are concerned, a brush holder is a brush holder is a brush holder, your local auto electrician should be able to supply you with a brand new Bosch brush holder for under $20.
If you need new brushes try and find a (non-genuine) set that has little flat terminals on the end in preference to the solder type. Better yet, buy one of each and after fitting the solder type one yo will know why I think the ones with pre-fitted terminals are the bee's knees.
If it isn't your brushes, on a low useage rate bike the circular contact areas on the rotor can grow verdigris and if can take a few secs to a minute for the brushes to polish that off. A spray of CRC electrical cleaner/lubricant will keep that nonsense at bay.
Next, check your low current terminals by breaking and making them, after that do the same for the high current connectors on the alternator and diode board.
If you have not cured the problem at this point, then you have a wiring fault int he alternator (most likely the rotor cause it is the bit that moves) or a developing fault in the low power circuit of the diode board.
Hint. For diode boards and rotors it is probably cheaper to swap out than it is to pay an auto electrician to find an intermittent fault. When the fault disappears the thing you changed last is the culprit, store it in a safe place for a month and then bin it if the fault has not reappeared.
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If the engine rpm's are too low, the light stays on .
You need to get the engine above the 2500 ish rpm area before it goes out on first start of the day .
The R65's and the Guzzi I have, have same Bosch charging system, do the same thing .
All bikes are different, so you may need to rev the engine higher to get the light out .
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I hate to disagree with Tony
But if the the rotor circuit is is open the gen light will fail to illuminate not fail to extinguish
First you will want to make sure it is actually charging after the gen light goes out when RPM is above 1200
If it is
The problem is that the diode board is not feeding the B+ to the rotor circuit (that is why the Gen light stays on )
Since it is intermittent I would start by checking the connection of the Blue wire to the D+ on the diode board
If that is not it test the diode board cold with a volt meter
and then check all the other connections and solder joints
Then it could be the voltage reg
Last likely is the stator
the are made from heavy wire and not as likely to fail
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I don't want to hijack the thread but this seems an appropriate place and time to raise the question.-
Sometimes the alternator light on the R65 comes on momentarily at very high revs. Whats that all about?
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I hate to disagree with Tony
But if the the rotor circuit is is open the gen light will fail to illuminate not fail to extinguish
You are of course 100% correct. I don't know what I was thinking other than perhaps conflating two entirely different faults. I have actually re-soldered the lead in wires on a couple of rotors - the failure mode being that the "potting mix" used to sort of secure the wires to the rotor fails over time, the wire(s) flex and ultimately fail. If you are lucky you can fish the broken end out and solder a new section of wire in and then stick it all down with a modern epoxy.
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Kookaburra, light coming on at high rpm's for a second or two, I'd check the alternator brush length .