Zapi COMBI ACE0 User Manual page 77

FOR and BACKING REV inputs.
Check the wiring of the BACKING FOR and BACKING REV inputs (use the
readings in the Tester to facilitate the troubleshooting). Check the
microswitches for failures.
A failure in the logic is possible too. So, if you have verified through the tester
that the BACKING FOR or/and BACKING REV doesn't change when you
depress / release the correspondant switches, replace the controller.
AF6ZP0AL - COMBIAC0 & ACE0 - User Manual Page - 77/79