I have a 1/2 Craftsman that is at least 7 yrs old. When I try to open it at the side door, the motor and light come on, the "trolley" thing runs down toward the door, but the door doesn't open. When I release the "open" button, the trolley runs back to the base. I notice one of the photocell sensors near the base of the board is out; however, I was having the above problem when it was on. I can't find the manual either online or in the files I inherited when I bought the house. I've read prior posts but can't figure out where all the parts are without the diagram.

Any suggestions? Thanks!
Alley

Sounds like the manual release on the trolley has been tripped.

It needs to be reset.

With a model number I can get you a manual on a similar unit.