Ever wonder how the BT Actuator works? When I had the circuit board out of the BT Actuator Control Box, I traced all the wires back to the locker above the sink. I posted a photo of the circuit diagram, and I'll try to copy it in here.
Keep in mind that your setup may be different, Bill R has noted there are at least three configurations on the SM. There is an Amel sketch of the wiring dated in the 90's, but it wasn't very close to the wiring on my boat.
Tracing all the wires helped me to finally find the bad connection. This issue was one where the BT had two problems, a bad limit switch, and a faulty connection of the hot wire to the on/off switch.