Arfa Daily wrote:
An alternate way of determining just
what it's doing, might be to set the toy up normally, with the correct
voltage applied, and then measure the voltage drop that's occuring across
this device. If you have another which is working, as I think you said you
did, compare by doing the same test on that one

I considered suggesting this, then concluded that there's no
(straightforward) way to discern between a failing Polyswitch and one
that's responding properly to a partially shorted motor winding, unless
the heat itself is a failure indication. I'd replace the Polyswitch
with a 1 ohm resistor, see how the motor runs, and compare the current
draw between the two units (by measuring the voltage across the resistor).

TM