I installed a new PTO switch on my White riding mower, model Number 135R616G190. When I list the knob(switch lever) upward to the 'On" position, then the blades start running. When I release the knob, then it it goes to the 'Run' position (middle position). When it does that then the mower blades stop running. What is wrong? Sam Coniglio www.samconiglio@yahoo.com 406-363-1677