Cut and pasted ( I know some won't apply to your new system )...... ...
maybe it will help ?
Troubleshooting a constantly on GEN lamp: If, when your ignition key is ON & the GEN lamp goes ON brightly, but it usually never goes out or only fades a bit when the engine is revv'd up, it usually indicates NO charging, or very little charging. A number of things can cause this, & there are various approaches to figuring out the problem. While you can use a test lamp if you know how to analyze things with it, use of a multimeter is probably easier, and you need to know how to use one. Read my article on them:
http://bmwmotorcycletech.info/multimeters.htm.That article covers both multimeters AND test lamps usage. You can possibly obtain a digital multimeter for FREE from Harbor Freight Company...they often give out quite adequate and accurate ones for FREE, upon ANY sale. Otherwise, they sell them for a variety of prices, depending on a lot of factors, almost always the price is LOW.
1. The brushes may be well-worn. Usually when the brushes wear one of the brushes will wear faster than the other. The snail spring on the brush usually can be seen to be "bottoming" on the white plastic brush holder. You can put a tiny piece of thick paper or other insulating item under the tip of the spring, which will allow the spring to press on the brush & not the plastic holder, until you can get around to installing new brushes. Brushes do not fail suddenly unless its flexible wire breaks ...which is rather rare. Typically, brushes get short enough that they make INTERMITTENT contact with the rotor slip rings; usually that intermittency is RPM sensitive.
2. Something in the diode board has failed. Bad connection, bad diode(s). This is not all that common, but happens. SOMETIMES the problem is caused by the owner removing the front cover, before FIRST disconnecting the battery! ....and thereby shorts the diode board in the cover removal operation. Now and then a diode board is fried by someone installing a wrong type of battery (reversed polarity terminals). SOMETIMES the motorcycle is the type with RUBBER diode board mounts, with mechanical mount failure with shorting. Rubber mounts are abominable for SEVERAL reasons: replace them with aftermarket METAL mounts.
3. The voltage regulator has failed. To test for that, either install another one; or, UNPLUG the VR, & in the PLUG, connect a paper clip or other item, between the opposing female connections. DO NOT connect to the solid BROWN wire! If the charging is now good, and voltage keeps rising with increased RPM (do NOT let it go over ~14.6 or so, absolute maximum 14.9), then the VR is almost for sure bad.
4. The rotor has OPENED (open connection internally in the rotor). This is common. Here are two additional tests (see earlier) to test for a bad rotor, and to eliminate that the brushes might be the problem. Put a piece of paper under each brush. Use an ohmmeter between the slip rings, should be very low resistance, a few ohms. As a second check, with the pieces of paper still under the brush, so brushes do not contact the rotor slip rings, use the ohmmeter between either brush and the chassis. If you get a low resistance reading, the rotor is shorted to its steel structure.
5. You replaced brushes; now you get a constantly on GEN lamp with ignition and kill switch ON, and it was OK before the brush replacement. You probably took the brush holder apart, misplaced the correct order & installation of the insulating washers in the Df brushholder section. Testing with an ohmmeter, D- and Df wires OFF, & paper under the brushes so they do not contact the slip rings of the rotor, are a quick method of determining things. ONLY the D- connection may be grounded.
6. You have mixed up the two wires going to D- and Df of the brushholder. The BROWN wire goes to the D- spade. Also see #5, above.
7. It is fairly rare for a stator to be bad. Usually that happens when someone removes the stator, IMPROPERLY using metal tools, and damages some of the wound-wires.
General notes:
Rotor failures are typically due to various types of aging. Rotors whose windings were unsealed, or sealed with lacquers or shellac, tend to fail due to stresses on the windings during larger RPM changes, typically when downshifting into first gear. Sometimes a rotor winding will short to another winding, or short to the metal magnetic pole pieces material. Now and then a rotor solder joint fails. I have seen TWO 'out of the box' rotors that were bad. One was a rebuilt, improperly tested, because there was continuity between slip rings and the magnetic metal, amounting to a direct short of Df to ground. Without measurements, you may not know what rotor you have. For the most part, rotors are being rewound with the later lower resistances. These work better than earlier 7 ohm rotors. It is not a great idea to install a 3.4 or 2.8 ohm rotor into a mechanical voltage regulator bike, without changing to the later electronic regulator in the plastic case; but, it will work for awhile with the mechanical VR. I suggest you avoid using a 2.8 ohm rotor with early stators; the charging output might be inadequate. This can be a puzzling thing, in trying to figure out what the problem is from low output.
Stator failures are NOT common; rarely from age failed insulation. Some failed because owners during removing & replacing rotors nicked the stator windings since to replace a rotor you must remove the stator housing. NOTE that the stator windings are done on multiple thin special varnish insulated sheets of steel generally called laminations. If you scratch across these sheets accidentally by using metal tools, you can have a stator that seems to work fine, but has "somewhat" REDUCED performance from what is called Eddy Currents.
Rotor failures, diode board and/or rubber mount failures, wiring failures, voltage regulator failures....and ignition switch and kill switch failures ....all are seen now and then. Often found are loose connections at the battery, or starter motor solenoid, or battery ground lead at the speedometer cable hollow bolt (DO NOT over-tighten that one!), or starter relay connections (or, internal in that relay). More on that relay in the next section after the horizontal line.
Failure to disconnect the battery before removing the outer cover of the timing chest, has caused electric sparks & failures of the diode board. Also be careful when removing the starter cover. It is MUCH better to disconnect the battery power before removing these covers!
Failure of the voltage regulator is usually indicated by poor or no charging or wrong voltage. VR failure is hardly the only failure to cause these problems. TESTING: You can easily bypass the VR, using a jumper across the opposing plug connections (NO connection is made to the BROWN wire!). That will produce maximum output from the alternator for any RPM that allows such, do not let the voltage get too high (14.6 is OK, absolute maximum is 14.9).
Occasionally a VR will fail in the Full Maximum Output condition; system voltage will be very excessive. 99% of the time the VR is at fault. Substitute a good VR.
Failure of the diode board is usually indicated by lower charging (lower watts) capability, or MUCH lower voltage output under load of such as the headlight (check battery voltage at ~4000 rpm with headlight on, and off). Just ONE "open" large diode will so indicate by vastly lowered charging with the headlight turned on, yet charging may be OK, headlight OFF.
Problems with the small diodes in the diode board rarely occur, and can usually be seen by poor charging or 'funny' GEN lamp indications, sometimes strange radio noises.
Almost anything that goes wrong with the charging system components can result in lower voltage, or low or no charging. Overheated, loose, or slightly dirty or corroded connections ARE COMMON. GEN lamps that can be seen glowing dimly at night while cruising is usually an indication of poor connections someplace, or several places. I usually see such a glowing lamp at night and my first assumption is that electrical wiring has never been cleaned or checked for tightness of connections, etc.
From the /6 to end of production there is a flexible printed circuit board inside the old-style instrument pod that the GEN lamp fits into. It can get microscopic cracks, and the lamp connection to the board can fail. You can carefully repair the board....or replace it (IF you can find a replacement!.....new ones NLA from BMW, but see KatDash on the Internet). Do NOT yank lamps out roughly.....press on the printed material with a fingertip & rock the lamp out carefully.
