Door will not operate unless you hold down button
I am presuming the following: is it that the door will not operate unless you hold down the button to "close the door"? And the button you are pressing is the hardwired wall button or control inside the garage correct? And if you try to close the garage door with the remote the overhead lights flash off and on or the motor make a clicking sound (about 5 clicks?)
The problem is either an obstruction of the safety sensors at the bottom of the door or, one or both sensor eyes are out of alignment. If you look closely at both safety sensor eyes on the part that faces into the garage, you should see a glowing LED. One side will be an Amber color and the other Green. If one is lit (amber) but the other is not (green), that is an indication that the beam is not being received by the receiving eye (amber).
If there is no obvious obstruction (check for spider webs, dust, try cleaning the clear lenses facing each other, etc,)
Try re-aligning the sensors. When they are properly aligned the Green LED will be lit. Now, check the motor for operation.
If you have difficulty getting the transmitter eye (green LED) to light, try closing the door at the wall button, then, pull the red emergency release handle to disengage the door.
Now, try operating the motor unit with the door disconnected while using the hand held transmitter. If the motor unit operates to the close position while the door is closed but not when opened, then that sounds like there is sufficient light entering the garage to "Wash" the transmitter beam out so the receiving eye does not get it.
Contact Chamberlain/Liftmaster for Sensor eye blinder shields that can be easily installed by you. (they just snap on)
If neither LED is lit, make sure that the wire to the sensor(s) has not been cut off at the sensor itself.
If that checks out, check the connection at the logic board. Make sure that both wires are securely connected.
If after checking all of that, and you do not have either of the LEDs on, then disconnect the safety sensor wires from the motor unit's logic board. Then take a 2" piece of bell wire and jump it across the two terminals for the safety sensors.
If the unit operates normally when using the hand held transmitter, then the problem is likely:
a) Bad safety sensors
b) Broken wire to one or both sensors
To check if the safety sensors are good:
Remove both sensors from their mounting brackets.
measure about 8" to 12" of wire from the back of the sensors and cut. You should have about 8 - 12 inches of wire on each.
Now, separate and strip the insulation from each and then match the white striped wires and twist them together, and do the same with the solid non-striped wires.
Take the sensors up to the motor head and connect the spliced wires to their respective positions on the logic board.
Now, Point the two sensors directly at each other (its okay if the clear lens part are touching each other)
Check if both LEDS are now lit.
1) If YES; then the sensors are good, the wire to them is broken somewhere; [FIX] replace the wires for both sides.
2) If NO: then the safety sensors need to be replaced. [FIX] Replace the sensors, contact Chamberlain / Liftmaster for replacement parts. You will need your garage door opener's model # which can be found under the light bulb or light fixture on the opposite side of the logic board.
Having the model # speeds up the parts search for you.
I hope this helps you out.
[I have been factory trained on residential and commercial garage door openers by Chamberlain / Liftmaster and have been providing installation and tech support on them for over five years. Prior to that I used to install and repair these units, and I've done that for nearly seven years.]
