On Mon, 16 Jul 2018 08:51:42 -0400, Wade Garrett
wrote:

On 7/15/18 6:14 PM, GOM wrote:
Garage Door won’t work. Motor “grinds” but the chain/retracting cable
does not move. Unit is a Chamberlain security 1/2 horse power.

Are the door's counterweight springs intact?

If one or both failed, the unsprung weight of the door exceeds the
motor's lift capacity and it may grind- or just lock up.
The parts are nylon, lubricated with cheap grease. The grease
hardens. The nylon cristalizes. The gears fail.
Common occurence, with no spring failures required.
Putting new grease in occaisionally will slow down the failure "a
bit"