The Nico auto-pilot was about the best wheel steering unit you could get back in 1978 when mine was made. The mechanical side of it was superbly built and is still almost as new. The electonics side is obviously way out of date. What I am trying to do is to marry-up a modern electronic package to the original drive unit.
I feel sure that someone must have tried this before now.
Had a Nico from 1975 - 1989. It never failed in that time but I vaguely remeber having cleaned the wire connections. It had a sprocket drive unit which seemed pretty straight forward with two wires for the clutch and two for the motor. I presume both were 12V.
It should be quite easy to drive this straight say from a Raytheon/Autohelm computer.
I think the Nico had a relais box for driving the motor in both directions, you wouldn't need that since modern autopilots have a MOS-FET bridge for that and in addition they do pulse the output to obtain better tourque at lower power consumption. I cannot see a reason why this wouldn't work just great with the old Nico drive.
I would think that most modern autopilot controllers would be bale to work with your neco drive.
What is your drive unit like?
Is it an electric sprocket drive, or a linear drive?
Or is it a hydraulic system?
If it is electric you should have four or five wires going to it or coming from it.
If four wires than two are for the clutch, which would nornally be totally isolated from the others. For a 12V clutch you should measure between 5 Ohm and 25 Ohm and you can tell the clutch from the motor by applying 12V to it, if the steering locks and nothing else happens you have the clutch. Check the current draw or measure the resistance as above, it will be needed to see what controller you could use.
If instead of locking the steering, the motor starts humming, but isn't moving the steering, you got the motor wires instead. Also measure resistance.
Now the motor could be simply between two individual wires in which case reversing the polarity will make it turn in the other direction.
Alternatively you may have three wires for the motor, one common that is connected to minus, and then the other are alternatively connected to plus to make it turn one way or the other.
A Raymarine (Autohlem) course computer, especially the new models 150 and 450 would be bale to drive about anything you might have. If it takes a lot of current or if you have 24Vm you would need the larger 450 or the older 300.
Very likely a cheaper integrated ST5000+ will do the job, but you'll need to measure your drive unit.
If you give me some more detail, I can most likely guide you further.
Know that problem, same with my boat. Drop me a line if you need some help in May. e-mail is email@example.com
In the mean time you may look what AP you like, I'm sure several will do fine with your drive. Since your boat is in Sweden you may want to also look at the Simrad Robertson units, I hear they are pretty good. Raymarine (Autohelm) has the advantage that they have most of their manuals online, that makes it easier to determine what may fit.