I replaced Autohelm instruments...... I installed an entire "network" IS20 system from Simrad 2 years ago and it NEVER worked correctly. I was Beta testing their junk for them. Ripped it all out and put in a Raymarine ST60+ system. Thats when I realized that the Autohelm wiring is the same as the ST60+. Nothing like re-wiring the boat TWICE. Just last week the ST60+ wind instrument quit working entirely. Its the control head, out for warranty repair, luckily within the 2 year mark.
The moral of the story? If I could go back to the bulkhead mounted Datamarine's or new Moor's, etc. I would. I don't understand the current trend to over-complicate these relatively simple devices. I fell into the "upgrade" trap. KISS on the instruments unless you are a competitive racer.
RT