Replacement magnetometer for yacht autopilot

I have a bit of an unusual application relating to my sailing yacht.

It has an auto pilot to steer the boat. The unit is a Simrad TP22 and it looks like the internal compass has failed, as the tracking goes into a completely random mode shorting after turning on.There are no stray magnetic fields or metailic item near and a similar (spare) pilot works fine

From watching your excellent vids, I believe I only need a 3DOF direction/magnetometor sensor.

Could this be used to replace the existing autopilots compass?

Before assuming the device is faulty, try a factory reset:
“No power to the TP32 press and hold Port. Tack, Starboard and Nav.
Power up the TP32 while holding the buttons in. The LED’s on the unit will blink Indication the reset.”
( Simrad/navico tillerpilor repair - Cruisers & Sailing Forums ( )

The compass is built in and directly controlled by the internal MCU, so a simple replacement is not an option.

The TP22 has a NMEA0183 input, and the ability to steer by GPS. It is easy to create NMEA messages using any small MCU and a magnetic compass. However the description is “Once interfaced [via NMEA0183] with a GPS or chartplotter, the Tillerpilot can steer using data from this source in addition to the internal compass…” [emphasis added] so that might not work if the internal compass is faulty. If you are using the NMEA input for some other purpose then you would need to combine the message streams. That becomes a little more complex, but still doable.

Another possibility is to us a MCU and a magnetic compass to integrate with SimNet (NMEA2000). This option will completely override the internal compass. There are libraries available for all the common MCUs. Connecting a new device to an existing NMEA2000 network is easier than with NMEA0183.


Thanks for the advise Jeff.
I will swop it out for a spare compass that I know is functioning Ok, before proceeding further