[greenman]

I would also check the sensor and magnet on the discharge beater, this will also switch the separator off

 

[greenman]

Your problem may be with the Left Hand harness with a broken wire, check wire number 302 (12 Volt power to solenoid on engine gearcase) and earth is OK. Please also check and make sure engine is charging at around 14 volts as low voltage will cause this and finally check engine relay panel for separator engage and swap relays. If all else fails with someone in cab for safety try hot wiring separator engage solenoid and see if this engages separator