My garage door, now seven years old, is the roller kind made of aluminium
segments, with a long thin electric motor inside the roller. The motor seems
to have been losing power: it will lower the door easily but is very slow at
raising it and stops when there is a slightly tight spot in the vertical
slides. The manufacturer's advice is of course to change the motor at a cost
of £300 plus. The normal output speed at the roller is about 10 rpm so there
must be some sort of gearbox inside the roller with the motor.
Two questions: firstly, does anyone have any experience of the failure modes
of these motors? It seems odd to me that it simply lacks torque. Secondly, I
wonder whether there might be a lack of lubrication in the motor/gearbox,
grease having gone stiff etc. Does anyone have experience of that?
I would take it down and examine the motor, but that is not at all a one-man
job.

Many thanks,

Stephen