On Dec 29, 7:39*pm, wf3h wrote:
OK *here's what it does.

it goes all the way down, sits there for a second then opens again.
It's a "Liftmaster" 1/2 HP motor. Checked the sensors and they seem to
be clear and operational.
Any ideas? Thanks much

Should be an adjustment for the 'down limit' on it somewhere, try
easing it. I had that problem, traced to slight swell in the ground
lifting the slab a bit. Mine, though, did not have a perceptible
pause before it reversed.

Harry K