For reference, I am assuming the switch you speak of is a plunger style.
And if it is Scag's Plunger-style operator presence safety switch is normal OPEN.
Meaning that you depress the plunger to CLOSE the connection (allowing current to go through).
If you were to use Scag's plunger switch to light up a light bulb, you'd have to PUSH it to get the bulb to light.
Released it's off.
And the switch's normal position is released (or off).
What you have to find out is whether the switch needs to be ON (or OFF) for the machine to function as you wish.
If it needs to be ON, then you can temporarily unhook BOTH wires and tape them together.
If it needs to be OFF, then you can temporarily unhook ONE wire.
If either of that fixes the problem, your switch is likely bad.
(btw Napa sells them)