[Richard]

Tony,

You stated when the circuit was disconnected, the breaker did not trip. This rules out a problem with the wiring going to the pump.

You did not report resistance readings between the hot and neutral wires on the pump. You did say the motor turns freely when the shaft is turned manually. This sort of rules out frozen bearings.

I suspect shorted windings in the motor. This would be confirmed with the resistance between hot and neutral AND between hot and ground.

I have no idea if the motor is removable and if it is, rebuildable.

There are some Grundfos booster pumps that fit in the same footprint. They work best if you also add a small accumulator tank. They are half the cost of the Headhunter.

I also believe @"Latitude 28" has implemented a cost effective solution to the HH.