Tenere charging problem
 

I am on an overland trip UK-NZ with my girlfriend, Claire. We are currently stuck with a problem with my Tenere (3AJ) in Wellington, NZ. Wondered if anyone would have any ideas.

The problem is that the battery just isn't charging. When the ignition is turned on the battery voltage drops about half a volt on my nearly flat battery and when the engine is started (using the kickstart) the battery voltage remains at this lower level. Revving the engine has no effect.

With a multimeter, I've measured the same voltage coming out of the rectifyer/regulator as seen at the battery and I've measured 6 volts a.c. between the white alternator windings. With the engine off, the resistance between white windings is 1 ohm (the smallest increment on my cheap little multimeter).

I have swapped the voltage regulator and battery with those from Claire's XT600E with no improvement and have checked all the wirings and connections until I am cross-eyed!!

Any thoughts would be greatly appreciated. By the way, am I right in thinking it is a permanent magnet type alternator?
Thanks, Mark

You are right in assuming that it is a permanent magnet alternator. The rotor(flywheel) has permanent magnets inside it which when spinning cause an emf (voltage) to be induced in the coil/s. Assuming the charging coil on the stator plate (white wires coming out)isn't fried, however a static resistance test doesn't show up weakness, you need to do a dynamic test while the engine is running.

2) You need to test the diodes in the regulator unit, to ensure they aren't fried, take the reg unit off and take it to a motorcycle electrical place for testing unless you know how to test if diodes are faulty.
My 2 cents
Good Luck

Thanks to DougM for his suggestions! The problem is now fixed and we are on the road again.

The alternator windings were burnt out even though the resistance measured correctly. Measuring the alternator output with the rectifyer/regulator connected misled me when comparing to the other bike. It has to be disconnected to get meaningful readings - I don't know why! Anyway, when I removed the windings the damage was obvious.

I replaced both the alternator and the rectifyer/regulator, as a failing RR is often the cause of a burnt out alternator. It can sometimes run fine for hours before it starts misbehaving. I didn't want to risk destroying my new windings.

Strangely the bike was unable to charge the flat battery during a 60km run, but a workshop successfully charged it. It took 3 hours before it started accepting the charge. I am now keeping a close eye on it just in case it dies!