Gregory Bender

Voltage regulator - Fitting a Bosch voltage regulator to a Magneti Marelli generator

Moto Guzzi V700, V7 Special, Ambassador, 850 GT, 850 GT California, Eldorado, and 850 California Police models

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Thanks to Gerhard Ziesemann for sending me this information via email. In Gerhard's own words:

Bosch Voltage Regulator on a Magneti Marelli Generator - will it work?

Most people tend to say it's impossible to make a combination of that. Some experts will even tell that you might damage all your electrical components. But they are wrong!

Truth is, it just doesn't work at all -- unless you change the internal wiring of the Magneti Marelli Generator a little. I selected the type VA14V25A regulator (BOSCH 0 190 350 055) because it appeared to be the best equivalent to the Italian original. On my '68 V7 this set has been working perfectly for more than 25 years:

Photo courtesy of Gerhard Ziesemann.

The two makes of generators differ in the position of the regulator. Magneti Marelli generators place the regulator between the + brush and the positive end of the field coils (via terminal DF), with the negative end of the coils connected to the – brush.

Photo courtesy of Gerhard Ziesemann.

On Bosch generators the regulator is placed on the opposite end of the field coils: Here the positive end is connected to the + brush, while the negative end is in contact with the regulator (via DF).

Photo courtesy of Gerhard Ziesemann.

The ends of the field coils can be identified by their cable lugs:

See number 6 under Assembly in Greg's Generator repair - Magneti Marelli for some illustrating pics of the DF terminal. The original wiring scheme for the Magneti Marelli regulator is shown there. Red marks the positive end of the field coils, black the negative end.

The conversion for a Bosch regulator:

Afterwards connect generator and regulator as indicated on the terminals and you will be glad to see it work properly.