The Lead unit for PS-1 does not use the switch for powering the Slave. 3 wires go to the slave for motor control assignment via the 4 pin tether. The 4th is coupler if the slave has it. The switch on PS-1 include smoke on/off and the coupler selection switch. PS-1 can only fire one coupler. You select Front or rear coupler with the switch. Usually it had arrows pointing. Smoke was labeled.
If they upgraded the Lead A to PS-3 you can not run the trail A. You need to do a PS-3 upgrade to the Trail as MTH did not support Slave PS-3 kits. Only Slave PS-2. Non are backwards compatible. PS-1 to PS-1, PS-2 to PS-2. PS-32 can work a PS-2 slave, but PS-3 diesel can not. So pictures to see what you have. G
