On Aug 24, 10:34*am, Andy wrote:
The garage door at my mother's house has an intermittent problem.

Sometimes it won't close. If I hold the button down, the door will go
down but when I let go of the bottom it starts going back up.

There isn't anything blocking the sensor.

The garage door opener is a Genie screw drive type that is about 15
years old.

What can I look for to diagnose the problem.

Thanks.

Maybe the switch is bad.

Does it work with a remote? You could try unhooking the wires from the
switch and tapping them together to simulate the pressing of the
switch.