Hi I have 2 speed Pentair whisperflo pool pump that includes the 2hp 071321S motor. My pool pump runs fine if I start in low speed and I switch it to high speed. My problem is when I start the pump in high-speed and then switch it to low speed, the pump shuts down. I have to wait a while and then the pump will work again. It works in all functions except switching from high speed to low speed. I have replaced the 35 micro farad capacitor that sits on top of the motor and that did not fix the problem. Any ideas of what can be causing this problem?