Boxerworks.com

Rob, yes it can happen. If it has continuity at rest and opens up at rpm, then that is a typical case of a false positive test.
Another example of why one builds up a spare parts cache.

Generator bulb replaced.
Alternator output restored.

Thanks.....

Ah, a typical boxerworks solution: great gnashing of teeth about the worst case scenario, while, in the end, the problem is the simplest one possible.

Yay!

MS, we have nothing to do, so we have to take advantage of this single chance to expound at length.

However, to be fair, the very first post had the answer. The rest of us just blabbered on.

Actually, reading through the thread I think we have enough information to have a pretty good go at diagnosing the situation,

Salient points are:

1. The fault happened at one point, prior to that everything was OK apart from an assumed battery failure (why else would you replace it?)... which probably has little to do with the current problem.
2. The measured 13.75 volts is healthy but was measured prior to the current problem so is irrelevant.
3. The bulb does not come on at all
4. The bulb has been checked and hasn't failed.
5. Since the problem started, the bike has failed with a flat battery on more than one occasion.
6. The failure occured during a period on inprecedented high ambient temperatures.

For the charge system to work, there must be a current flowing through the rotor. This current initially flows via the bulb. In the absence of the current flowing there will be no charge. This is confirmed by the fact that the bike has failed with a flkat battery. It follows, therefore that if you restore the current you will solve the problem.

Common causes for the current to fail are:

1. Failure of the bulb (already eliminated)
2. Failure of the rotor (pull the brushes away from the rotor and check for resistance between the slip rings. No continuity means a failed rotor, no resistance at all indicates a failed rotor. You are looking for a resistance of around 3.5 Ohms... you need a good multimeter to measure this. Rotors tend to fail more in high ambient temperatures so this is my favourite
3. Brushes worn out. This is normally more intermittent so if you experienced no problems prior to the current failure its less likely.
4. Wiring failure between the bulb and the regulator. The current path is from the negative side of the bulb to the voltage regulator. Disconnect the regulator and make a connection between the blue wire (D+) and ground. If the bulb lights, you have proved this part of the circuit.
5. Voltage regulator failed open circuit. disconnect the regulator and connect a wire between the two outer connections on the socket. If the charge lamp comes on the regulator has failed. Be aware that the opposite doesn't hold true... if the bulb doesn't light, there is definitely another fault but the regulator isn't necessarily OK. You may need to repeat this check when you've got everything else working.
6. That leaves the wiring between the regulator and the alternator. A black wire. If everything else has checked out, than there must, just about by definition, be a break in that circuit.

Once you have solved the 'Charge Lamp Mystery' hopefully everything will be back to normal... if not, there's another fault and you have to start from there.

Rob

Rob, did you miss John's post above?

R65john wrote:Generator bulb replaced.
Alternator output restored.

Thanks.....

I think Rob posted his reply so it could be printed and put in a safe place for all who haven't done THAT yet.
As we read thru the many historical posts on charging or lack-of, it seems that would be quite useful.