LEMANS 1000 CHARGING LIGHT - SOLVED

[lazlokovacs]

hi, calling all old tonti gurus,

first symptoms,

at idle charging light flickering on and off, actually toggling with the neutral warning light and wild downward swings of the voltmeter, reaching behind the instrument dials and wiggling stuff about seems to cure it.

now (4 days later),

-on closer insepction battery does not appear to be charging when engine is revved.

-In key on but engine NOT running situations, it is a 50/50 toss up whether the charge light will come on.

I'm going to go through all the steps and check everything when I get time,

in the meanwhile can anybody hazard a guess?

thanks as ever

[guzzisteve]

I would check charge lite connections & clean slip rings on the alt rotor w/light sandpaper taking off the glaze. No voltage gain or stability then start checking components, rotor, stater & diode board.

[Wayne Orwig]

The connection at the light is critical to running the charging circuit.
Clean the connections and inspect the wiring to get the light to work reliably. Then see if it is charging.

[Groover]

Also check/clean connections at the voltage regulator.

[Chuck in Indiana]

DeOxit is your friend.  My first guess is the connection at the charge light, too.

[Kiwi_Roy]

A clue is the Neutral warning light, there is no reason it should flicker, my guess is you are loosing Voltage at the common point (red wire), check all fuses and connections for tightness and perhaps dismantle the ignition switch and clean the contacts.

You are loosing power to the Voltmeter which also happens to be the supply for the two lights that are flickering.
My California II has similar wiring, it's a constant battle to keep it working if I want to run heated gear.

[lazlokovacs]

thanks,

checked all the connections behind the instruments, bulb is getting 12v consistently (though possible that it wasn't before), if i unplug the wire from the bulb to the rectifier and ground it, the warning light comes on.

FWIW now there is no flickering, just a 95 percent of the time refusal from the charge light to come on (ignition on engine not running)

so I'm thinking the rectifier (which is well grounded) may be toast?

[Kiwi_Roy]

Trace the generator light through all the way to the alternator grounding out each terminal as you go to make sure the light goes.
It goes from the light to 61 terminal of the rectifier, 61 is jumpered to D+ terminal internally from there it's wired to D+ of the regulator, it goes thru some internal circuitry to DF, from DF it's wired to DF on the alternator, it goes thru the brushes and rotor to chassis. Some point along the way you must be loosing contact. The rectifier doesn't really do anything until the motor is running.
The regulator must have a good ground to turn on the transistors that pass the light current from D+ to DF terminal.
As an alternative to grounding the terminals you can measure the Voltage relative to chassis.

I sent you a PM
Roy

PS
I was recently asked to look at a non charging Lemans, I found both brush wires were severed.

[lazlokovacs]

seems that I have power all the way to the alternator,

if I bridge the slip rings on the rotor, my charging light comes on, (ie an earth is reached)

so I guess thats an open circuit on the rotor...

anyone seen this before?

and special thanks to Kiwi_Roy for a lot of good information

[guzzisteve]

Slide a matchbook cover under brushes to isolate rotor & check ohms.

[lazlokovacs]

yep, it was the rotor, swapped it for an old one from a beemer in my friends shop..

charging nicely now, light is back on when it should be..

thanks for all the input

[Two Checks]

BMW rotors are not the same as Guzzi rotors.

[lazlokovacs]

thanks for the info

in this case we held the two in our hands and they were the same size, same weight and had the same windings, same threads and same part number... and the bike is now charging as it should, so the differences must be minimal.

[Stevex]

thanks for the info

in this case we held the two in our hands and they were the same size, same weight and had the same windings, same threads and same part number... and the bike is now charging as it should, so the differences must be minimal.

That's the clincher, and they're both made by Bosch, no?

[guzzisteve]

Maybe the BMV had a Guzzi charging sys on it cause it puts out a bit more.

The difference is 1/2mm