Well OK, I was wrong. Diodes are NOT required.
While I thought the 4th line was a data input, it was really another high / + power. I found this out after trying a diode on one leg, which did not work at all how I though it would.
So after some trial in error this is what I have.
On the ribbon cable starting at the end opposite the red #1 line we have:
#4 = 10 degree turn
#3 = turn to starboard
#2 = 1 degree turn
#1 = turn to port
Connecting #4 to either #1 or #3 does a 10 degree turn to the indicated direction. Connecting #2 to #1 or #3 does a 1 degree turn to the indicated direction.
On the relay card from left to right you have the following connections
below, relays numbered 1 to 4 with pins a,b,c on each relay.
1A #1 signal wire and daisy wire to 3A.
1B #2 signal wire and daisy to 2B
1C No connection
2A #3 signal wire and daisy wire to 4A.
2B #2 signal wire (daisy chained from 1B)
2C No connection
3A Wire connected to 1A
3B #4 signal wire daisy chained to 4B
3C no connection
4A wire connected to 2A
4B wire connected to 3B
4C no connection.
You will need to solder a 3" ish length of wire onto #4 signal wire so it will reach the 3B connector. 22 gauge wire is all you need. I stole some from the Garmin
plotter cable that was not being used. (I'm frugal).
While the relays effect the heading sensor when energized, it's of such short duration that the boat does not have time to respond before the wheel turns in the correct direction. Oddly the direction turned by the relay changes depending on heading. But it's very minor.
I wear the remote on a lanyard around my neck. A lovely hack for those still using the old Autohelm 3000