Weird Electric Motor Behavior

The rotation is due to the phase shift of the magnetic field generated and the capacitor is responsible for that...It sounds like you installed the rotor in a reversed position first time and eliminated the phase shift the second time...or the capacitor could be failing, I would replace this as standard procedure anyway....

I have a new word! Ferkling! Consider it stolen.

There is a centrifugal operated switch in the end bell of the motor.

This switch is closed when the motor is stopped,and open when it reaches a certain speed.

If this switch is not closed when stopped,the direction of the motor is unpredictable,and most times will not start,but simply hum.

If you give the rotor a little nudge,it will start in the direction of the nudge.

Listen for a "click" when the motor stops.

If you do not hear it,check the switch for proper operation.

Sometimes the leaf spring gets bent during disassembly and the contact does not close when reassembled.

All of the above does not apply if it is a split phase permanent capacitor motor.

Thanks to you three for taking the time to respond. I remember you, SolarEagle! Unforgettable handle! Anyway, 1) no centrifical switch in this unit. 2) rotor can only be installed one way as only the one end is threaded for impeller. 3.)cap is not polarized (terminals indistinguishable). I tried to "implant the appropriate memory" in the cap by hooking it up while rotation was correct but it didn't work.

Point 3. Because it is a AC cap. That memory story only made me chuckle, what are you talking about. The cap is used as a coupling device to couple the AC it receives with a delay to the winding and the delay is dependant on the size of the cap. The positive 1/2 of the AC cycle goes through the cap a split second later still as a positive pulse and when the polarity of the AC cycle goes negative it goes through the cap a split second later still as s negative pulse. The "time length" Of the split second depends on the size of the capacitor.

An open capacitor or bad wiring to the capacitor will give same symptoms as a bad centrifugal switch,and since the motor does not have a centrifugal switch,I surmise that the capacitor or wiring is bad.

Since it ran fine before seal replacement,I suggest checking your wiring.Of course,the capacitor could have gone bad.

The capacitor determines direction of rotation by creating a phase shift of the current/voltage between the start/run windings.

If it goes open or shorted,it can start in any direction,depending on which half of the A/C cycle arrives first.

It can happen any time.And you know how Murphy works.

Did you take a photo or made a numbered note of the way the original wiring was connected to the motor. It can help if you give us that information and a photo of the wiring as it is now. Looking at you capacitor comment the chances are good that you did wire it wrong.

I tried reversing the connections to the cap just in case. In made no difference. That is why I clutched at the atraw of a memory. That said, the cap terms are indistinquishable and so are the wires that need to be connected to it.There is no reason to suppose they need to be connected one way or the other.

Ps. I have replaced hundreds of capacitors of all kinds, sometimes new, sometimes used, and have never seen this happen. Also, cap was tested on a meter with a dedicated setting and tested ok

Did you make nites or took a photo of the wiring before you disconnected it? Take a photo of how you connected it now and post it here.

One likely reason I can think of is the stator has been put in reversed so that the drive end is now the non drive end.

The motor relies on a phase shift of 90 deg between the start and run winding to go and if the 90 deg is in the other direction then the rotation will be reversed.

It may also be that the centrifugal switch if it has one is not making contact and the motor starts dependant on the inrush of the power to the run winding.

Ok well, by seeing the topic I came into the tread.

Ok, cool.

We will be able to be more helpful if you will take a picture of the motor data plate and post it here,then we will know exactly what type motor you have...otherwise,it is a pot shot guessing game.

If you cannot photograph it,list all the info on the data plate and post it.

With having a capacitor but not a centrifugal switch, you likely have a Permanent Split Capacitor (PSC) motor. Reversing the connections on the capacitor itself will not have any effect. It is the relationship of the capacitor to the main or auxilliary windings that determines the rotation direction.

If you remove the capacitor altogether, you are effectively also removing one of the windings, so the rotation direction becomes random on energization. It might alternate, it might not, there is no knowing.