toller wrote:

About a month ago my Liftmaster 1265 stopped running. It
would just hum for about 2 seconds and stop. Liftmaster
said the limit switch has been overrun, so I played with
that. When I move the limit back, the opener hummed for
2 seconds, paused, and then hummed for 2 seconds with
a slightly different pitch.

Someone here said the problem was probably a leaking
capacitor. I took the cover off, but the capacitor
looked fine. But when I touched the capacitor the
opener suddenly started running. It was okay for 2
days, then stopped again. I touched the capacitor again
and it ran okay for 5 minutes, then stopped. Now
touching does not help.

Did you remove the cover without disconnecting the AC power first?
That can be risky, not only because of the potential for electric shock
but also for the opener to start accidentally and grab your finger or
hair.

I'd first disconnect the AC and see if the connections to the motor
capacitor are loose. Reseat any push-on spade connectors, and tighten
any screw eyelet connectors. If that doesn't help, then you may have a
bad motor capacitor or a bad connection elsewhere. Vibration from the
motor can make solder joints crack on the printed circuit board (PCB),
but the cracks can be microscopic, so some technicians simply resolder
almost everything (start with connectors and larger, heavier component
connections).

Since the motor capacitor is an oil-filled one, it can be tested fairly
well with just an ordinary volt-ohm meter -- see www.repairfaq.org for
instructions and also for safety advice. These capacitors are
available from almost any electrical supply but not from electronic
supplies, which rarely carry oil-filled capacitors. Liftmaster is made
by Chamberlain, which also makes Sears Craftsman openers, and Sears is
sometimes cheaper for parts.