Garage door opener won't work. Motor housing turns partial revolution but looks like transmission jammed. Motor broke from mounting screws. Stanley Premier, came with house, maybe 25 years old. Time for a new opener?

Either the motor has seized or the door itself has jammed. Unlock the manual release (Usually a cord or lever hanging down 1/2 way along the track) Sometimes if its a side mounted motor, the lever will be at the side of the motor .Pull the cord or move the lever, and the door should be able to be opened manually. If its stuck then you will need to check the tracks and rollers on the door and door frames to see whats jamming it. Repair or replace as required. If the door comes up freely, that will prove its not the door jamming.Try leaving the door in the manual position and turn the motor on. The door wont open or close itself when in the manual position, but the motor should run. If it still hums, I would say the motor has seized. Sometimes, its cheaper to get a new opener / motor complete assembly rather than a replacement motor on its own. Check with the manufacturer and or supplier of the door opener to confirm.

With the garage door up pull the release cord to disingage the garage door it self in the up position. You can skip the disengaging step, But,It saves ware and tear on the motor.

Then using a step stool you will find limit adjusting plastic slots/screws on the side of the opener.

The left screw is for garage door down.

I would turn the left screw clockwise 1/2 turn or less. then activate the remote opener. noting which way the latching mechanism moved. and so on.

It may take a few adjustments with this proceedure to get it perfectly closed. Then activate the remote to re-engage the garage door it self.

Also, LiftMaster has a web site that you can check out.

Your trolley may be jammed against the bolt just in front of the motor unit. If so, loosen the chain enough to relieve the strain on the chain and then run the opener until the door is closed. While the door is closed locate the 'up limit' control on the side of the motor unit. Turn this control 2 full turns in the opposite direction of the arrow printed on the cover. Tighten the chain.

You have somthing broke inside the opener. It's time for a new one.

Make sure the trolley is not jammed against the bolt just in front of the motor unit. If it is, remove the bolt and run the opener until it closes. With the door closed locate the 'up limit' control on the side of the motor housing. Turn this about 3 turns in the opposite direction of the arrow printed on the cover.

Your motor may be working too hard anad ripping the reset button on the garage door,
Try increasing the power on the unit ( should be some type of dial.) or the door may be jamming up somewhere, Try disconnecting the opener from the door and see if it goes up easily, the door might need service

The trolley (the part that moves back and forth and is connected to your door) of your opener is most likely jammed against the bolt just in front of the motor unit. You can remove the bolt or loosen the chain until your unit will run. Once the door is closed find the 'up limit' on the side of the motor unit and turn it about 3 turns in the opposite direction of the arrow printed on the cover. Now replace the bolt or tighten the chain. Whichever you first did.

TIME TO REPLACE THE GEAR KIT PARTS ARE AVAILABLE IF YOU ARE A REASONABLE MECHANIC IT IS A DOABLE REPAIR - FOLLOW THE INSTRUCTIONS!!!!!

2 flashes is a safety eye issue, but you problen is most likely that the chain is not sync with the limit setting. Take the bottom off the gear and sprocket assemble and rotate center limit srew until it is in the same position as the trolley.

It sounds like you did a really good job! My Craftsman 1/2 hp gar. dr. opener has a red reset button on it on the l/h side as you are looking at the light/motor from the garage door opening. You have to take the light cover off to be able to see it. My reset button is on the same side as the ground wire. You might check the ground wire while you're there. I really hope that this fixes it for you (and me). I'm quite sure it will as you know your way around the garage door opener already. Good Luck and Let me Know (Please) if it fixed it or not. If I think of anything else, I'll let you know. Have a Good Day!