no pressure switches in this
very basic
switch at hyd control handle linkage
a contactor on the contactor panel

thats it
if it runs 100% of the time then one of those is shorted out
(slight possibility that a wire may be connected wrong but i'd bank on the shorted switch or contactor)
also check the switch adjustment, it may have an old style roller arm switch against a detent on the hyd spool, those will get out of adjustment or if they get dirty that can cause problems.