Forgot to mention that idling is all the time normal if I disconnect the speed sensor plug at the wheel. There is only no speed reading, no tacho reading and no automatic switch off from the turn signal. The rest is all OK. This is to make the headaches complete.
During tracing the wiring I found some sensors shared connections (reference and/or return?) with the speed sensor. This probably explains why you loose tacho reading when speed sensor disconnected.
Richard
2018 Roadster 3.7 1966 Land Rover S2a 88 2024 Royal Enfield Guerrilla 450 1945 Guzzi Airone
