NAC-3 Autopilot and RF25N Rudder Sensor
Posted: Fri Jul 24, 2026 8:18 pm
I’m commissioning a new B&G NAC-3 autopilot on “Justified” (Erie PA) using a Vulcan 9R, Precision-9 compass, and RF25N NMEA 2000 rudder feedback sensor.
The only issue preventing commissioning is the RF25N. During rudder calibration, the displayed angle doesn’t change smoothly with wheel movement. It sits at one value, then jumps several degrees, often showing nonsensical numbers (for example, around 62° with the rudder centered). Calibration cannot be completed.
To rule out installation issues, I removed the RF25N from the boat and rotated it by hand. It exhibits the exact same erratic behavior, so it doesn’t appear to be caused by linkage geometry or mechanical installation.
The NMEA 2000 network diagnostics show no dropped frames or communication errors, and the RF25N is the only device on the network providing rudder angle data.
Has anyone seen an RF25N behave this way? Was it ultimately a defective sensor, a firmware/configuration issue, or something else I should be checking before I replace it?
The only issue preventing commissioning is the RF25N. During rudder calibration, the displayed angle doesn’t change smoothly with wheel movement. It sits at one value, then jumps several degrees, often showing nonsensical numbers (for example, around 62° with the rudder centered). Calibration cannot be completed.
To rule out installation issues, I removed the RF25N from the boat and rotated it by hand. It exhibits the exact same erratic behavior, so it doesn’t appear to be caused by linkage geometry or mechanical installation.
The NMEA 2000 network diagnostics show no dropped frames or communication errors, and the RF25N is the only device on the network providing rudder angle data.
Has anyone seen an RF25N behave this way? Was it ultimately a defective sensor, a firmware/configuration issue, or something else I should be checking before I replace it?