I replaced the gears and as per directions I put door in closed position, cycled motor to open position but it won't cycle back to closed position so that I can install chain. Motor hums and then stops. There is no blinking and the eyes on the sensors are aligned. If I move the limit switch it will run but not change direction. I could use any help offered!Thamks
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Re: Liftmaster 1/3 HP opener won't close
Strange, was going to say eyes not aligned but you say they are. try over-riding by holding down wall pushbutton or jumping from red and white terminals. Did you increase down force. Are limit switch terminals moving, If it hits one, it should go back to other,
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The problem is not the chain, it is the plastic gear in the unit of the liftmaster Garage Door 1/2 Hp.The plastic gear is not engaging, although it sounds like it is working.
You will have to replace it with a new one, then the liftmaster Garage Door 1/2 Hp will be able to open up once again.
Once you open and remove the old gear, Be sure to thread the screws in all the parts before you install them. Pre-threading them once would really
help. Secondly, label the wires on the back of the opener before
lowering it to the ladder, so you can put them back in their proper
10 beeps signal a blockage. This is what happens: the control board monitors the current absorbed by the motor; when a mechanical fault or something else is blocking the movement the motor automatically tries to overcome it by delivering more power, in the process absorbing more current; this current triggers the warning and the door system goes in danger mode - it returns the entire unit to the original state (fully closed or fully open). This happens like that so if someone gets caught it won't gets squished.
In your case the damage is internal, in the gearing between the motor and the chain sprocket - it occurred when you have tried to install the chain. You will have to completely dismantle the motor and its gearing to see what broke in it and fix it if possible. Worst case scenario: you will need a new unit.
See if the trolley is jammed against the bolt just in front of the motor unit. If so remove the bolt and then run the opener until the door is closed. While the door is closed locate the 'up limit' control which is on the side of the motor unit. Turn this control 2 complete turns in the opposite direction of the arrow printed on the cover. Remember to replace the bolt.
If the door starts to close and the main light flashes 10 times and the door reverses to the open position it is a problem with the door sensors. Make sure they are pointed at one another and they each have a small light that must be on and not flickering.
If it starts to close but reverses and the main light does not flash 10 times it is possibly the RPM sensor which is a small printed circuit board just in front of the motor.
You say it only opens two feet?? Then closes?? If I may if you a little bit more costly option. Dont replace the gears. They used to be really good 8 years ago but the way they make the gears now there too soft and often strip out much faster. I would suggest that you do what we call a motor head change out. Take off your old chain drive motor head and buy a new one. Pretty simple. Two things though one always make sure you put the new one in with the door down. And the traveler in the down position ( The traveler is the metal thing hooked up to the chain) but far and your gear that you have it sounds to me that you dont have the gears close enough.. but 100 percent on that but a door should never close on it own. It's not safe.