faulty fuel warning sensor

OK, thank’s for that

If your fuel-sensor is the thermistor type it will be inside a metal jacket with tiny slots.
If the sensor is supplied with 12 Volts and the fuel level is low it can get red hot and fuse within seconds. This would happen on the California models with an electric petcock. Normally the lamp limits the current to less than 100 milliamps so it doesn’t get over hot but if the plugs are swapped by accident it’s toast.
Panasonic make a sensor identical to the one used on an early Triumph Tiger pump, that will work in your Guzzi
The Panasonic part No is ERTLG12N7 but you might get one easier from Triumph

Thank’s for that Roy, I’ll check it out.

Petrol is a liquid and therefore cannot burn.
The fuel delivery system and ignition system turn it into a vapour which does.
To make it explode requires a sealed system.
This is why the old Steam Racket’s stealing your petrol makes the situation more volatile.