Gen light not lit.

[(RIP) Sam Johnson]

Hi,

The GEN light in the intrument panal is not lit even with the ignition on. The bulb is OK and the bike starts and runs but I am not sure if its charging. or what

Any idea's please, could it be the Diode Board?

Sam

 

[nud1e]

Rotor

I speak from bitter experience - most probadly rotor has failed. In the interim, keep the battery on charge and don't venture to far. If the revs seem to be rising on the tacho without the engine speed increasing, head to the nearest
battery charger.

Rotor is easy enough to replace, if you have the extractor bolt - cut the short leg of a 6mm hex key if you haven't - put the bike in 2nd gear, stand on the rear brake while tighten up the rotor bolt and wait for it to explode of the taper. Take u/s rotor for rewiring.

 

[cookie]

almost certainly the rotor. take off the cover, put some paper under the brushes & check with a meter. no continuity between bands & it's shot.


my advice would be not to just tighten the extractor to remove rotor. tighten, then tap the end with a hammer, repeat as necessary.

as nud1e says, use a sawn off allen key or similar [or the proper tool, it's cheap].

DON'T use a nail, they bend & then jam into the crankshaft

and no, i've not actually done that myself i'm happy to say

ps. rotors are interchangeable with guzzi & morini items.

 

[fritz]

Doesn't the light stay on when rotor goes ? or does it stay on if it's overcharging ? Anyway as mentioned its POP to check, and POP to change......like a paralever then....not

 

[Frank Warner]

Rotors fail open circuit most of the time (80%?) and that will mean the light does not glow.

Easy check - take the front cover off and short the rotors' slip rings - the lamp should light. If it does then your rotor is stuffed. If the lamp still does not light then - faulty lamp? faulty brushes (these contact the slip rings and ware out)? faulty wiring (blue wire from lamp under steering head fractures)?

 

[Howard Millichap]

Doesn't the light stay on when rotor goes ? or does it stay on if it's overcharging ?

No. The light is fed through the windings of the rotor. It goes out when the generator starts charging (back EMF). So if it's not lit when the engine is off, it is undoubtedly the rotor windings that have failed. Usually happens around the 40000 mile mark.

 

[Frank Warner]

The light is fed through the windings of the rotor. It goes out when the generator starts charging (back EMF).

Nothing to do with back EMF.

The light provides a small current to the rotor (from the battery through the key switch and the engine kill switch) to establish a magnetic field. Once the alternator starts producing an out put the field diodes supply current (and voltage) to the rotor - thus the lamp goes out as the diodes and stator provide the energy (actually more energy) that the lamp was providing. No back EMF is used to turn the lamp off!

 

[Howard Millichap]

Nothing to do with back EMF.

The light provides a small current to the rotor (from the battery through the key switch and the engine kill switch) to establish a magnetic field. Once the alternator starts producing an out put the field diodes supply current (and voltage) to the rotor - thus the lamp goes out as the diodes and stator provide the energy (actually more energy) that the lamp was providing. No back EMF is used to turn the lamp off!

I'm only quoting a BMW "technician". What's the difference anyway? One current cancels out the other. Same thing really.

Anyway, doesn't alter the fact that the lamp is fed through the windings, so when the lamp is off when the ignition is on, the rotor's phuqed!

 

[Howard Millichap]

(these contact the slip rings and ware out)?

And while we're getting technical, don't you mean "wear"?

 

[Frank Warner]

I'm only quoting a BMW "technician". What's the difference anyway? One current cancels out the other. Same thing really.

Anyway, doesn't alter the fact that the lamp is fed through the windings, so when the lamp is off when the ignition is on, the rotor's phuqed!

Man proves black is white and gets run down at the next zebra crossing.

Sorry about the wear,.

The energy to illuminate the lamp does not come from the windings - it comes from the battery. The winding provide a path for the current to flow - but that current comes from the battery. OK? The difference is the understanding of how it works – that can be of use in figuring out what is wrong in other circumstance, if your understanding is wrong then you cannot reach a correct solution for other problems.

 

[AndyT]

Don't you just love this forum...

... everyone tries to be helpful and it can so easy be misconstrued by the way its written but the message usually gets over.

Actually both of you are wrong because its the ratio of the flux capacitor to the angle of the windings that causes the bulbs to grow...!!

Have Fun

AndyT

 

[nud1e]

Re: Don't you just love this forum...

...
Actually both of you are wrong because its the ratio of the flux capacitor to the angle of the windings that causes the bulbs to grow...!!

AndyT

and that, children, is why we have daffodils in the spring.

 

[Howard Millichap]

Re: Re: Don't you just love this forum...

and that, children, is why we have daffodils in the spring.

Not round 'ere we don't. We 'ad 'em in mid winter this year, before the snow!

I'm sorry, I though it would be obvious that the lamp was fed through the windings from the BATTERY because it comes on when the engine is NOT running.
It's always been my biggest failing......assuming that most people have a modicum of intelligence.