:welcome:
One at a time you are going to have to go through the mowers safety switches and relays.
Safety switches work in pairs.
Seat + PTO
Seat + parking brake
Parking brake + lap bars
plus
PTO all by itself with engine not running.
The kill wire is a ground circuit so if the kill wire is grounding out to the engine or mower anywhere it will stop the sparks.
We don't get Ferris down here so I have no service information for them, but the proceedue is the same for every mower.
A wiring diagram will be of great assistance as there is no standard wiring colours for mowers,
If there is a bunch of relays, buy a new one then substitute one at a time.
I find it easier to use a test lamp hooked up backwards ( ground wire on battery + and probe looking for ground in the harness ) but make sure you disconnect the wires at the coils first because if they see battery voltage for the briefest time they will be toast.
Before you start, make sure the PTO switch is off and if you can get at it a good spray with your goo of choice ( WD 40 etc ) and work the switch back & forth as they do get dusty.
All the wires on the PTO switch, except the 2 closest to the knob are safety wires.