Make sure you are connecting the wires correctly. The solid white wires go to terminal 2 and the white wires with black tracer go to terminal 3. There is no way to check the sensors other than to hook them up to the opener. They should be marked with a small decal. One is the 'sending unit' and the other is the 'receiving unit'. The light on the sending unit should be on all the time and the receiving unit only lights when they are pointed at one another. It sounds like the receiving unit has a short causing the light on the sending unit to go out. See if you can take them back.

I am at my wits end. I have a brand new Chamberlain opener and the sensors will not stay aligned (I have tried and tried, even with a laser leveler but nothing works). I was told that I could by-pass them by taping them together, eye to eye. I tried this last night and it still doesn't work. I don't need the sensors, is there anything I can do? Please help!
Thanks,
Greg

gmani:
I don't understand your post. you say that the sensors "will not stay aligned". I interpret this to say that they work when initially installed, but then move and no longer see each other (so the door doesn't work properly). Then you say that when you put them right next to each other (and bypass the safety feature) they don't work (even though "alignment" is taken out of the picture).

If they don't work when in very close proximity to each other (assuming they are wired correctly and there are no cuts/breaks/shorts in the wire leads) then they don't work at all. If it's a brand new opener then return them.

This is a safety feature that is integral with the computer logic board. There is no way to disable the requirement to have working sensors connected and still have the door operate without having to manullay hold the wall switch for the full closure of the door.

hope this helps.

gmani check the connections at the terminals on the back of the motor unit. If they are not tight the vibration when the motor runs could be causing your problem.

I have a similar problem. I had a brand new garage opener installed about a year ago and it all worked fine. Recently, my remote stopped closing the door, yet it opens fine.

When I hold down the button on the wall (directly connected), the door closes. The power is set to the max and there are no difficulties sliding the door for the motor.

I suspect the issue is with the sensors. One is ALWAYS yellow while the other is always green. I even unmounted them and held closely together (still wired) to check the alignment issue, but same result. One thing to note is there was some work done near sensors that produced A LOT of dust.

Is there anything I can check or do to fix this?

Thanks in advance.

vzelenko:
If the sensors are operating properly, the sender light will be on all the time, but the receiver light should only be on when it is aligned with the sender. If the beam is broken, i.e. something blocks the reciever then the light should go out. If you're finding it on all the time and can't make it go out then it sounds like it might be a logic board problem. when the work was done, is it possible that the circuit got overloaded and tripped the breaker or something like that? the PC logic boards don't like electrical spikes and it may have damaged the board.

Hope this helps.

I have a similar problem, the door will not close unless the wall switch is held. I have moved the sensors physically together, one has a yellow light which is always on regardless of alignment (is this the sending unit?). The other has a green light which, in this reconfigured (close together) arrangement is on solid (i.e. aligned). But the symptoms are unchanged.
The travel (door down direction) is about 6 to 8" then stops and reverses (the door itself is released to eliminate any binding problem). A small yellow light on the back of the motor flashes four times then goes out and then repeats the four flashes.

The flashing light is giving the code for misaligned sensors but that can't be as you describe it. I would have to say bad sensors. The light that stays on all the time is the sending unit and the other is the receiving unit.