Brand new motor cycles on/off every second.

[BigDave]

Sounds like the motor's the same (it's not the UCT1102 is it?). Check the wiring, check the voltage, check other wiring connections that may have been disturbed. A bad connection can be the cause of high resistance which would drop voltage at the motor.

[PoolDoc]

One possibility: the pump is wired incorrectly -- there are many ways to do so. Another is: the pump is set to 120V but supplied with 240V.