First, you connected SPEED- to a Ground?
If you read with a multimeter voltage should be around 5-7v while moving, near 0 or 12v while standstill.
The board have 2 resistors (R60 and R66) for a total of 320 ohm on this line.
ISO is only 100 ohm (stronger pull down).
But this should not cause an issue.
If you think this is the issue you can:
1-The thc R65 can be used to put something around 100-200 ohm in parallel to make the pull down stronger.
2-Or solder R66 to make it sort, then you will have 120 ohm (R60)
Yes Speed- to ground. I used a 2.2kohm as pullup to the 12V.
I don’t have more possibilities to test before we’re done harvesting (lack of time )
When king winter kicks in, I will spend some time to upgrade the system. And by then it would be great if this small fix could be done on the AIO board,
I ended up using the system with a fixed speed. not ideal, but it’s working