North Lost and Found Again
On our way down the river to Rocky Pointe Marina for our haul-out, the autopilot simply refused to follow an automatic heading.
Losing our autopilot makes cruising a lot less comfortable. Hand steering the boat is more than feasible, but the long hours at the wheel are tiring and take one of us away from performing other functions on board.
We consider the autopilot a "cruise essential" item, one that we must have to go cruising long term, long distance.
In order to do its job properly and steer or navigate the boat by itself, the autopilot needs to know where "North" is, and for that ours uses an electronic compass.
Looking at the autopilot heading display (the angle of the boat compared to magnetic North), I could see the electronic compass was wildly off, and even worse that it was registering turns the wrong way.
A compass rose is graduated from 0 to 360 in a clockwise direction, with the North being at 0 (the top), East at 90 (the "03 o'clock" position on a clock face), South at 180 and West at 270. This means that when the boat is in a turn towards Starboard (a right turn) you will observe the compass' heading increasing. Similarly when turning to Port the compass heading will decrease.
Well, on some Starboard turns or adjustments, I could see the compass heading decreasing. In reverse, I could see it increasing during Port turns. It would also jump apparently randomly with no real relation to the actual boat heading.
After double and triple checking that we hadn't store anything strongly magnetic too close to the compass I was sure nothing had changed so tried getting the compass to find its lost North back.
There is a procedure to re-calibrate a lost compass: It involves making constant speed turns until the compass' electronic brain can understand where magnetic North is, and calibrate itself accordingly.
So for a while I looked like a drunken sailor, going around in circles trying to get the compass to finally re-calibrate itself. Unfortunately it never did, implying a much graver problem than a simple calibration issue.
Running some diagnostics I concluded the fault was likely the compass itself, and not the whole autopilot computer it feeds info to. Quite a good thing too, as neither are available anymore, though the compass can still be found on the second hand market. The autopilot's computer rarely comes on the second hand market, and commands crazy prices when it does. Buying an old second hand autopilot computer makes a full replacement of the whole installation a very realistic alternative. Not a cheap one when much of the autopilot's ancillary components and wiring must be changed as a result. Luckily it looked like a simple and "cheap" second hand compass would solve our problems.
A quick email exchange with our electronic specialist who installed the whole new bridge package a few months ago confirmed my diagnostics. His advice was to find a certified used electronic compass unit, and he kindly provided me a link to one he thought would be fine.
I bought it immediately via eBay and received it 3 days later. Installation was very simple, just a matter of taking the old compass out and splicing the new one in with 2 wires.
A quick autopilot computer setup later and we were back in business, receiving good solid electronic compass indications.
Last thing to do was to re-calibrate the electronic compass, once again going around in circles on the river. This time the calibration took and the calibrated values are then automatically saved in the compass' brain.
North is found again and Enfin can safely go cruising soon.