I have developed a strange issue with my Moto Guzzi Galletto. There is a red light on the headlight cluster that goes out when you throttle the accelerator indicating that the battery is charging. The light comes on at idle speed which is how it should run. However in the past few days I am noticing that the lights doing it’s own thing intermittently. Occasionally works as it should but then just stays on. I have put a multimeter to the Dynamo- there are 3 cables coming out of the Dynamo (black thick cable, white thin and red medium thickness) which all go to the regulator. I don’t seem to pick up any voltage from the Dynamo and was wondering if I am doing this wrong. Any ideas what could be the fault?
(Index of /schemas_electriques/monos_et_autres)
Wiring Diagram here - the regulator is also the starter motor relay
Thick Black - Starter Motor
Red - Voltage Out
White - Field Coil
With the engine running you should have voltage on the red wire to earth, if not see if you have voltage on the white wire to earth. If you have nothing on the white wire its likely the regulator is damaged. worth doing these same checks from the regulator connections to exclude broken wires.
The green wire on the regulator is from the starter switch to trigger the starter relay in the regulator.
THe relay terminal with the pink wire connects the regulator output to the battery and ignition switch
The regulators from this era are notoriously unreliable. There are plenty of modern reliable solid state dynamo regulators available but you would need a separate relay (50 to 70 amp) for the starter motor.
Hope this helps
Russell
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Thanks Russell, I did some digging and from the archive library my schematic is the last pdf. It appears that the black thick wire is the main power cable going into the regulator (30h) the red and white are field and the other connections. So I put my probes on the black and got a proper voltage. I am now unable to replicate the fault as the battery is charging as it should so until I can again get this issue I am still in the dark whether it’s will be the Dynamo or regulator that’s on its last legs. Thanks for your help😁