Battery light on when bike is off

[rdolan]

Newbie K bike owner. Long time airhead. 

Ok, I'm stumped. 88 k75s, see fi you guys have a take on it:

New WestCo this season. Stayed off the bike for a month (injury), and I come back to find it dead. I do not try to start it knowing how easy it is to weld the relay.  I hook up the tender overnight.  I notice the battery light ON when I hook up the tender. Curious, but I figure, sure...the battery's charging.  Come out to find it has not charged.

I take the WestCo off the bike, try another charger and get 3V into it and nothing more. Diagnose faulty battery. Also maybe faulty charger. 

New Battery Tender, and new Odyssey installed. Odyssey is at 13.2V. Here is the curious behavior:

Battery light is ON when the bike is off. NO matter key position or kill switch position.
Bike starts strong, starter motor stops spinning when is started like it should. Battery light is OFF when the bike is running. 


Thoughts, anyone?

[rbm]

Defective regulator on the alternator now, possibly because the defective charger killed the electronics on board.  Measure the battery terminal voltage with the engine running above 2000 RPM; you should read 13.5V or higher.  If you read 12V or lower, diagnosis confirmed. You must swap in a new regulator.

[rdolan]

Thanks for the quick reply and advice, Robert. I measured V at 2k RPM at 12.3. Just popped in a new regulator and symptoms remain: the battery light remains on when bike is off and V remains at 12.3 at 2kRPM.

Any next culprit advice? Perhaps starter relay?

Thanks

[rbm]

Are the electrics on your bike modified by yourself or a previous owner? 

It's sounding like the exciter circuit is getting power continuously from the battery (which would cause a drain).  The exciter should only get switched power, and that comes through Fuse #1 via the power in the instrument cluster.

A defective regulator might have a shorted diode that allowed leakage current from the battery.  But you've replace the regulator proving this is not the cause.

The only thing I can think of is that the electrics on the bike have been modified and the exciter circuit is connected to continuous power.

The lack of charge voltage is still pointing to a defective alternator.  This could be insufficient current in the rotor to setup the required rotating magnetic field, it could be broken wire in the stator, it could be still a defective regulator (although that is a minute possibility).  Have you checked out those possibilities.

[rdolan]

One mysterious PO mod I don't understand:  https://www.dropbox.com/s/6r0d6jnywd6egnk/2015-07-30%2019.58.29.jpg?dl=0


Looks like I'll pull the alt off and go get it bench tested.

[rbm]

From the picture, it looks like the PO is grabbing +12V off Fuse #3 and piping it to Fuse #1.  That's where you're getting the constant +12V to the exciter circuit.  This cute mod is also constantly powering a number of other switched circuits on the bike.  This certainly must be draining your battery, if not also causing other weirdness.  Have you tried to remove that wire to see what happens?

[rdolan]

Thank you for your attention to my saga. Very kind advice. I appreciate it.

The strange mod is for some running lights, not a jumper. I took off the gas tank and traced it. Symptom of battery light on when bike is off remains.

So, I've removed the alternator and will take it in to be bench tested/rebuilt. Will post back here.

best
ry