GEN light fun /7

[nhlkats]

It started with the headlight not turning on on my 77' R100/7.
Traced it from bulb, back to headlight relay, back to control board, back to handlebar switch, disassembled the switch to find that the HI/LO/PASS flipper switch contact plate no longer had contact with its target. Simple fix, tada, headlight works again. Great...

Now you're asking what does this have to do with the GEN light?

Upon reassembly, I crossed two contacts on the headlight relay (like a dolt) by mistake with an unfortunately placed screwdriver, and a nice big bright spark flew up in my face ( :nono which is why you should follow procedure and disconnect your negative term b4 doing electrical work). Had my 2yr old dry cell Westco on the charger at the time. This was yesterday.

Today, I noticed I am no longer getting a 14v charge at +3000rpms. I also noticed a steadily decreasing voltage. 12...11...10. I turn around and start heading home. I also noticed the red GEN light go on when I'm above idle, solid bright when I was on the throttle. These are all new symptoms as of today. Otherwise, bike ran great, and did get me home safely, although voltage on the gauge was near 10.0v by the time I got home.

So I am not getting a charge to my battery from my alternator. Could this be related to my mishap yesterday? Could this be completely unrelated, just coincidental timing?

My initial plan is this:
1) Record current battery voltage.
2) Attempt to charge battery using charger.
3) Record voltage after charge.

If I find that the 2nd reading is not north of 12v, I can conclude that I damaged my dry cell battery with my big spark yesterday inside the headlight bucket?

If it does restore charge to 12v or above, what do I test next?

Thanks in advance. :brow

[cjack]

It started with the headlight not turning on on my 77' R100/7.
Traced it from bulb, back to headlight relay, back to control board, back to handlebar switch, disassembled the switch to find that the HI/LO/PASS flipper switch contact plate no longer had contact with its target. Simple fix, tada, headlight works again. Great...

Now you're asking what does this have to do with the GEN light?

Upon reassembly, I crossed two contacts on the headlight relay (like a dolt), and a nice big bright spark flew up in my face ( :nono which is why you should follow procedure and disconnect your negative term b4 doing electrical work). Had my 2yr old dry cell Westco on the charger at the time. This was yesterday.

Today, I noticed I am no longer getting a 14v charge at +3000rpms. I also noticed a steadily decreasing voltage. 12...11...10. I turn around and start heading home. I also noticed the red GEN light go on when I'm above idle, solid bright when I was on the throttle. These are all new symptoms as of today. Otherwise, bike ran great, and did get me home safely, although voltage on the gauge was near 10.0v by the time I got home.

So I am not getting a charge to my battery from my alternator. Could this be related to my mishap yesterday? Could this be completely unrelated, just coincidental timing?

My initial plan is this:
1) Record current battery voltage.
2) Attempt to charge battery using charger.
3) Record voltage after charge.

If I find that the 2nd reading is not north of 12v, I can conclude that I damaged my dry cell battery with my big spark yesterday inside the headlight bucket?

If it does restore charge to 12v or above, what do I test next?

Thanks in advance. :brow

I don't think you could have hurt the battery. You need to see why the alternator isn't charging. You must have crossed red with something else. Black would just try to run the starter motor. The rest of the contacts would have just turned on lights or done nothing. I would say that most likely, you didn't cause the problem.

[nhlkats]

update:

Bike has sat untouched since initial post 4 days ago.

Voltage at battery was 12.4v just now.

When turning key to ON position, the GENERATOR lamp was not lit (the GENERATOR and OIL indicators have always been brightly lit before starting up until now).

Upon starting the bike, the voltage at battery remained a constant 12.4v.

When revving to above 3,000rpm, the voltage at battery remained constant at 12.4v.

When revving, the GENERATOR lamp became bright, but then once I sustained a constant engine rpm, it was less bright, but still on -- I think (hard to tell because it is still light outside).

Battery sitting on charger now.

Is it possible that something got jostled in the headlight bucket that could have f/x this?

Where should I start trouble shooting?

[20774]

Seems like you should check the usual culprits...you're not getting any output from the alternator. Either the rotor has gone open, the regulator has stopped regulating, or the diode board is kaput. I seem to recall recent threads on problems with the charging system.

[nhlkats]

Kurt - Been reading them. But in the back of my head, I am still thinking about the work I was doing last weekend in the headlight bucket before this charging problem arose.
Is it at all possible that the symptoms I am experiencing could exist with a properly functioning charging system, and have manifested from a problem in the headlight bucket? In other words, is it possible that it looks like a charging component problem, but it could actually be a wire in the headlight bucket?
Or can we safely say this problem is for sure a charging system component, and no matter what I did in the headlight bucket, this problem is separate?
You see what Im getting at?

[20774]

I see what you're saying... Well, it's obvious that there's no charging going on...you've established that. I'm no electrical wizard, so I suppose it's possible that something in the headlight shell could be part of the problem. Since you were messing in the headlight and the charging system didn't work after that but did before, then I'd certainly investigate the headlight shell again.

But I'm wondering if what happened in the headlight shell took out a piece of the charging system. So, there may be two problems...a dead element of the charging system and a malfunction in the headlight shell (either temporaray or still present). Right off hand, I can't think how the headlight wiring directly connects to the charging wiring. There must be some commonality...I'm not near any wiring diagrams right now...

One of the simplest things to do is to check the resistance of the rotor. I suppose a large dose of power could have surged through the rotor windings and caused it to be open. IIRC, voltage goes into one slip ring, through the windings, out the other slip ring, and then to ground. There are also resistance checks on the stator that can easily be done as well. After that, checking the regulator and diode board get a little more complicated.

[nhlkats]

Is BMW special tool rotor puller part No 123 600 needed to gain access to these parts in order to administer these tests?

In the Clymer manual, it appears that testing the rotor involves removal of the rotor, which requires this special tool.

Want to make sure I'm prepared :brow

[cjack]

Is BMW special tool rotor puller part No 123 600 needed to gain access to these parts in order to administer these tests?

In the Clymer manual, it appears that testing the rotor involves removal of the rotor, which requires this special tool.

Want to make sure I'm prepared :brow

You can test everything without pulling the rotor.

[OHScot]

Um maybe check all the fuses first. Think simple it was just a brief short. :stick

[20774]

After looking at the wiring diagram, I just don't see any connection to "sparks" in the headlight shell and the charging system. The only thing that's somewhat related is the charging light in the instrument pod. You've already indicated that it's lighting up, but not in the correct modes.

As mentioned, you don't need to pull the rotor. Carefully lift the brushes and place a business card, etc., between them and the slip rings. Now you can measure the resistance from one slip ring to the other.

The B+ terminal on the diode board should be at the same potential as the battery. When the system is properly charging, the voltage at this terminal should be 13.5 to 14v. Make sure that this wire (between B+ and the +post on the battery) is continuous...if open, then the output of the diode board can't get to the battery. Of course, the voltage regulator is an important part of the circuit as it regulates the output as well.

[nhlkats]

Found the diode board's B+, but cannot find it's D+ terminal. Where is it hiding?

Is the center rotating part, the very center fascia that faces forwards of the what is the slip rings, is that supposed to have a decent sized nick in it? I have a gouge in mine...but it looks like it could be intentional for alignment purposes?

update

Did several of the suggested tests today.
Recall: GEN light wont come on when bike off with ignition on.
Once bike is on GEN lamp comes on brightly when throttle revving, and dimly when maintaining engine speed.
No charge coming to battery.

Clymer manual Alternator and Voltage Regulator Quick Test:
Jumped alternator's D- to DF.
While bike off but ignition on --> GEN light brightly on.

Read voltage b/w diode board B+ and alternator D- --> 0v.

Slipped business card underneath both brushes so they didn't contact the slip rings, measured resistance between the two slip rings --> OL --> open circuit?? in rotor itself or where?

Clymer Manual Stator Test:
Measured resistance b/w the 3 terminals that the electrical connector plugs into --> 0.5ohms for each pair. The manual states to measure the electrical connector itself, not the terminals that the connector plugs into, but I got no reading on the connector, and the proper reading of ~0.5ohm when checking the terminals.

Diode Board B+ terminal voltage --> 12.99v

Diode Board B+ and Battery+ resistance --> ~1.5ohms

Measure voltage at brushes:
Front right brush --> ~7v
Back left brush --> 0v


Was unable to perform the following two tests today:
1] Momentarily connect brush positive to battery positive and check for voltage rise which indicates good alternator (but since brushes aren't outputting much...this test probably won't conclude much?)
2] Clymer voltage regulator test: connect voltmeter b/w diode board D+ (WHERE IS THIS THING??) and ground (found this one :clap ). Start engine, record voltage.


Despite not performing the last two tests, with the info that the slip rings are not continuous, and that the back left brush is reading 0v, can any conclusions be drawn here? Any further tests I should do? Is this implying a faulty rotor?

On another note, I noticed today I have a drain with the battery negative detached. Its almost 1v. Peculiarly, with ignition on (and battery negative still detached), the drain disappears. But turn ignition off, and drain of ~1v. I tracked it to the ignition switch inside the bucket, of which one of the leads coming to one of the terminals is draining about 0.2v only when the ignition is off and battery detached.
Something else to figure out :D

[20774]

Have you seen this wiring diagram? It helps understand the system a little better. D+ is the main output on the diode board...

http://www.buchanan1.net/charge.shtml

The fact that you have an open rotor isn't good. I'd confirm that...if it pans out, then you could get a rewound one from Rick at Motorrad Electrik or send him yours and he'll rewind it. BTW...not sure about the "nick" you're talking about. There is a large groove between the two slip rings, but I'd hardly call that a nick. Other than that, I don't know of any unusual marks on the very front of the rotor, the parts that spins around.

As for the brush voltage readings...current flows into one brush (probably the front), through the rotor windings, and out the other brush which then is connected to ground. That's basically illustrated in the above URL. D- is equivalent to ground. Sounds to me like that would explain why you get +V on one brush but 0V on the other brush.

I'd focus on the rotor...the wire that's wound onto it has developed an open circuit.

[nhlkats]

Kurt, Jack, Rick (@MotoElektrik) --> Thank You.

Just replaced the rotor, and it seems to charge now. Will go for test ride and thoroughly check everything out.

Anyways, thanks again.

[PGlaves]

Since the new rotor solved the problem I'd be satisfied it was a faulty rotor. But why?

There are clues for future reference. First, key on, engine off the light didn't light. Since the rotor is in series with the bulb this signals a problem with the rotor circuit. That circuit is: battery to ignition switch to kill switch to bulb to regulator to hot brush through rotor to ground brush to ground.

This symptom could mean a bad connection in any of those wires, a burned out bulb, a bad regulator, bad brushes, or an open rotor.

But ... when the engine was started the light did come on. This would be impossible with a truly open rotor. But the rotor tested open when stationary.

My conclusion is that there was a broken wire in the rotor. That would make it open. But when the rotor was spinning the broken wire moved enough to ground itself, allowing current to flow and light the bulb. Probably grounded at a spot where the magnetic field in the rotor built up to only minimal, thus still no charging.

The one possibility inside the headlight shell would have been a loose connection either to or from the bulb. But since the isolated rotor tested open you can probably rule this one out.