I had a failure of the 5 rpm gear motor actuator which I use to control my projector focus. Focus control is needed as the Qume Q5 focus is not temperature stable. it's a 24VDC rated little can type brushed motor I operate on 12V. It stopped working when it got cold, even at 40F the motor would not start. I use a modifed 2 channel IR receiver to control the gear drive, since I already have IR extender control of the projector.
I took it apart the failed gear motor and found the motor, brushes and commutator are clean, and the motor starts and runs freely at 12v in both directions.
So I'm thinking that the black grease which covers all the metal gears, and the worm drive which is on the motor shaft gets so stiff in the cold that the motor can't spin up. Spin up is not aided by the two pole commutator.
I'm thinking of cleaning out the grease and putting a bit of ATF on the gears. I'm also going to boost the voltage. I think there's some 19 or 21VDC for the projector I can use. This is not a high stress application and it only runs for maybe 30 seconds a day. Any other ideas?