Reply To: Faulty Nexus Wind Vane

I was interested, we had the Nexus 2 on a previous boat. There is a fantastic description of the operating principles used in the Nexus 2 on https://hackaday.io/project/179262-logging-sailboat-instrument-data/details. Scroll down to the section on the wind sensor and enjoy, it is really rather clever!
You did not describe whether the wind direction data was also affected by your fault or simply wind speed. The description makes it clear that the same pair of infra-red sensors determine BOTH wind speed and direction. If both direction and speed are similarly faulty then the problem probably lies with the sensing system, if only speed is affected (and you suspect that it is reading low) then the propeller bearing may need attention. If just wind direction is incorrect then the vertical (vane) bearing would be worth a look. The sensor head outputs two signal lines which run down the mast to the Nexus server, both carry the wind speed data, only one set is required for wind speed BUT the difference between the two encodes the direction data. So there could be a wiring problem between masthead and the server. Problems most commonly occur at mechanical connections so I would start by checking / re-making the connections where the two signal wires are attached to the server.
If you can find a friend with some electronics knowledge then he / she could narrow the problem down quite easily by connecting a scope to the wind terminations at the server.