I might have misread the problem. Just to verify, you have a two speed, dual voltage motor? The reason I ask is that personally I haven't seen a two speed pump being able to be run at either 120 or 240 volts. I've seen dual voltage, single speed pumps, and dual speed, single voltage pumps.
Going off that, assuming you have the dual speed, 240V pump, I would initially suspect that you aren't getting 240 volts in low speed. The problem with this theory is that the pump usually won't run, but just sit and hum.
One other thing to consider is perhaps you have a bad capacitor. Many times a dual speed pump will have 2 capacitors, one for low speed, and one for high. If you have two capacitors, either they will be both found in the removable back plate, or one will be in the back plate the other being in a housing attached to the side of the motor, or both attached in separate housings on the side of the motor. Since these are start capacitors, the usual problem is that the motor won't start, but if you get it spinning it will still run.
Last thing i can think of is maybe your centrifigual switch, located in the back of the motor, and is used to disengage the capacitors when the motor reaches 70% of it's rotational speed. If this switch isn't opening up at full speed, it will cause the capacitors to remain in the circuit, generate lots of heat, draw more amperage, and could actually burn out the motor. |
