Micro Metal Gearmotor MP 2371 Locks Up

I recently purchased two of the metal gearmotors. I mounted a pololu wheel on them and mounted them to a chassis. To test them out I connected them directly to 4 AA batteries (6 volts) and heard a clicking sound from one motor as soon as I powered it up and the other one rotated. With no root cause found the motor would randomly work. It then became sporadic with both motors working on and off. I have tried to isolate the problem by removing the wheel, removing the gearmotor from the bracket, and trying multiple voltages. Not sure if there is any significance, but I do have 3 ceramic capacitors between the terminals: one .1microF across terminals and two .047microf from each terminal to motor case. Any thoughts would be appreciated.

The micro metal gear motors are very sensitive to soldering time. If you keep the soldering iron to the contacts for more than a second, you’re likely to start melting the plastic that holds the contact – and that contact in turn holds the brush that drives the motor on the inside! This happened to me when I had to de-solder a capacitor I soldered onto the contacts.

My guess is that, while soldering the contact leads and capacitors to that motor, enough heat made it from the contact to the plastic, so that the contact moved and the brush is not making a good connection on the inside of the motor. The instructions for this motor actually mention that they are sensitive to soldering heat, but I was surprised by just HOW sensitive they are!

Thanks for the reply. I will remove the motor from the gearbox and see if it still locks up. I can imagine if the brushes aren’t supported they may be randomly hanging up on the commutator.

Solved…so far. When the motor was locked up it always made a clicking noise as if it was attempting to move, so I looked closer at the gearbox. I found that the motor pinion was randomly coming in contact with a gear right above it. I was able to turn the problem on and off by moving the interfering gear while spinning the gears by hand. To correct the problem I pressed the motor pinion on a little further on both motors and so far so good.