Dead Motor Replacement?

I had a PS1 F59PHI that had the same problem. The motor on one of the trucks was stuck. After turning it by hand using the flywheel it works like normal.

Do some more testing before you deem the motor dead.

FWIW, testing on blocks is a poor test.  Almost any dual motored diesel with tach driven cruise control will have the controlled motor running before the "slave" motor in that scenario.

Did you check the wiring between the motors, they should be in parallel.  Did you try the roller test at higher speeds, say 60 scale MPH?

If the motor gear and motor size (365 or 385) it can be used.  But you need to check for imbalance.  Don't discount that the tach motor is the problem motor and starts turning to soon.  I have seen this in 2 PS-3 diesels.

The fact it is bad in forward but fine in reverse could be gear lash or some other issue in truck too.  G

Spray CRC Lectra-Motive cleaner into the failing motor while it is running.  It is non-flammable and will clean the commutator of the debris from the brushes.  We use it at MTH and 50% of the time motor current will drop in half.  I check the motor current by disconnecting the board and using a filtered DC power supply with an ammeter.

Thanks for all the great feedback. Pretty sure the motor is dead. When I turn the flywheel by hand everything is fine. And the engine was working perfectly for weeks before there was trouble. It WAS jerking going forward and smooth in reverse but then the non-tach motor just quit. No matter how I apply power to the engine it won't turn. So I'm going to treat it as if it's dead, unsolder the wires and connect these to another motor to continue to troubleshoot. If the replacement motor spins, then I'll drop it in.

After I disconnect the wires from the current motor, is there a measurement I can make (voltage) across the wire leads that tells me that the motor is getting the correct power? It should be if the other motor is working.

Thanks

@Scott J posted:

After I disconnect the wires from the current motor, is there a measurement I can make (voltage) across the wire leads that tells me that the motor is getting the correct power? It should be if the other motor is working.

It should be getting EXACTLY the same power as the other motor since they're wired in parallel.