This is probably too long so...
We just started a 2-4 month cruise and after 2 weeks our autopilot failed. I had bought an almost current generation Raymarine plotter a year and a half ago and after some fiddling I got it synched in with my late 90's Raymarine heading sensor, course computer and autopilot. It was working well and even tracked routes in the plotter, until last week.
Here's what happened: We were leaving the Ft. Myers beach mooring field headed to Marco Island Florida when out in the Gulf I engaged the autopilot for the 30 mile run to Marco. The autopilot engaged in auto mode and when I placed it in track mode the boat made a hard turn to the left and as I went to place it in stby I noticed the rudder indicator on the autopilot control head indicated full left rudder. After placing the autopilot in stby I turned the wheel to the right to regain course but the boat did not react, it kept turning left. I immediately turned all power off to all nav equipment (I have a switch on the helm) and regained control of the rudder but not until the boat had turned 270 degrees. Fortunately we were cruising at 7.5 kts not our sometimes 15.5 kts and we were in open water with no other boats or day markers nearby.
In troubleshooting the issue I noticed my Ray plotter had lost positioning and heading and no depth was displayed on the plotter but was available on the depth gauge. My Garmin plotter worked normally but no depth was displayed on it either. My Garmin plotter receives depth from my Ray plotter via NMEA 0183. The autopilot head displayed STALK FAIL.
I pulled out my electronics wiring diagram that I made when I installed the new Ray plotter last year and starting troubleshooting while the Admiral drove (without autopilot). After 2 hours of troubleshooting I could find no loose wire or anything suspicious.
Once at anchor in Marco Is (Smokehouse Bay) I called Raymarine and after some tests determined the autopilot head (ST6000+) had failed and was interfering with the sea talk & NMEA comm. After disconnecting the autopilot head all other functions came back, depth displayed on both units, heading displayed and positioning on my Ray plotter.
Ray has not supported the autopilot for some time and will not repair the unit. About 6 months ago I had to buy a new LED screen for this unit on e-bay. Used units are available on e-bay but I really didnít want to throw good money after bad hoping these 15 year old units would keep working. The problem with replacing the autopilot with a new one is the new stuff doesnít integrate well with my old sea talk gen one and NMEA 0183 comm protocols. So in order to install a current gen autopilot I have to also replace the course computer now called an actuator control unit and the heading sensor. 2 boat bucks for this new equipment.
The next day while at anchor we walked to a nearby West Marine for some other stuff and I asked the salesman if he knew of a local marine electronics company that may have an old autopilot head. He gave me the name of a place in Naples about 15 miles away. I called them and though they didnít have an old autopilot head they did have a new Ray kit that included everything I needed including the cabling. Even better the owner of the company said she lived in Marco Island and would deliver the unit to me at the dinghy dock without charge. So Susan at C-tech marine electronics in Naples made good on her promise and the next day in about 2 hours I had the new stuff installed and we were on our way.
Weíre now in Key West, have 150 miles on the new unit and itís working well. However itís not working 2 boat bucs better than the old unit.