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Brian, Architect
Category: Home Improvement
Satisfied Customers: 3123
Experience:  Licensed Architect- 17 years, L.E.E.D. AP
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My 7yr old Chamberlain Liftmaster door wont close without

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My 7yr old Chamberlain Liftmaster door won't close without multiple tries. Both sensor lights seem align fine, with steady lights on. LED on the motor does not lit, flashes couple of time upon re-press the button on remote. Manual lift/close the door is sooth, too.

Any idea what the problem is? I do observe that the light on the motor flicks if the door is opening or closing. Thx.

Hi, my name is XXXXX XXXXX I will be helping you today.

Please try the following test:

Press and hold the wall button and see if the door will close.

Customer: replied 4 years ago.

Tried it before. It stops frequently, closes less than 1 foot. If I try press too many time, the motor power will go off (light goes off), power comes back after couple of minutes.

I know you have manually operated the door but perform the following tests:

First, I would close the door and then disconnect the door from the trolley and operate the door manually. The door NEEDS to roll smoothly and not bind on anything and it NEEDS to be balanced and stay at any point you stop it. If the door wants to go down by itself the springs are weak or broken and at fault; have a qualified service technician fix/ adjust them as they can be very dangerous to work with since they are under extreme tension.

Second, operate the opener WITHOUT the door attached and see if it operates correctly. The trolley will fully go up and down if working properly.

Performing these tests will help narrow down whether the door/ tracks or the motor unit is giving you the problem.

Please let me know what you find from these tests and we can proceed from there.
Customer: replied 4 years ago.
Hi Brian, Just got home and did one test as you said, disengaged trolley and the door can go up and down, can stop any where.

Can't test further. Just found out now both sensor lights are out. Don't know what caused it. Or it's the result of progressive case? I noticed first couple of days I only need to press twice to complete close the door. Later days it stopped more often till yesterday it closed only few inches for each time I tried to close. This has been for 2 weeks. Can you confirm that the sensors need to be replaced? I measured the voltage on the receiving side of sensor, it shows only 0.16v but at the motor side it reads 6.15v. What does it tell you? Does it mean the wires between motor and sensor got bad?


Bill, The 6v does sound should be between 5-6v at the opener. The low reading at the sensors is not good.

Since both sensor lights are out this is saying that the sensors, or the logic board or the wiring to the sensors are the problem. Sometimes the wires get corroded at the connections and you could cut, strip and reconnect the wires to the sensors. You could also have a short if a staple has worn through the wire.


If one or both sensors are blinking, the sensors are misaligned.

If one of the sensors is out, the door sensors typically need to be replaced.

If both sensors are out, the problem is typically a bad logic board or bad sensor wiring.

You need to look closely at the wiring, to the sensors, to see if it they are broken or pinched by a staple. You can test the wires with an ohm meter for continuity or two wires shorted together.

If the wires appear to be good, remove the sensor wires from the terminals on the logic board and check for voltage across terminals 2 and 3 on the logic board. If you have 4-5v you will need to replace the sensors. If you don't have 4-5v between terminals 2 and 3 and the opener is plugged in, the logic board is bad.


Customer: replied 4 years ago.
Thanks Brian.
It's so strange that over the night, both sensor lights are back on. I did not pull any wires last night.

So I tried with the door disengaged, the trolley still can't close all the way. I took the reading at the sensor, it stays around 5.7v while the trolley is stopping and closing. I also measured voltage at Term 2 n 3 wIth sensor wire unplugged from motor, terminal 2 a d 3 also reads at 5.7v. Does that mean the logic board is bad, or the sensors? Also, does the light flicking while motor is running mean anything to you? My other opener light does not flick.

Thanks again

Hi Bill,

The logic board is good if you are getting the 5.7v at 2 and 3. The sensors or wiring is the culprit and that is good news....less money to fix.

The flickering is telling me a loose wiring connection or that the sensors themselves are not securely attached and wiggling. They need to be secure so that they don't move and disrupt the beam signal.

I would think about replacing wiring and/ or sensors if they are already securely attached.

Customer: replied 4 years ago.

Thanks Brian. I'll try to replace sensors first. The wires are in the wall, hard to replace them.

Sounds good. I think you will find that replacing them will fix your problem. If you don't mind exposed wiring, just abandon the existing wiring that is buried in the wall/ ceiling. Good luck with it.

Customer: replied 4 years ago.
Sorry Brian, had to ask one more question. Watched a video on YouTube today, it suggests that if I place a jumper between Term 1 and Term 2, the door should be able to close. I tested it with door disengaged and sensor wires were unplugged, sure with leave the jumper in there, it still acts the same. This test should bypass the safety sensor, right? Now the reading between Term 1 n 2 is 23v. Does this test result proves the logic board is faulty? Thx, Bill.
Hi Bill, yes I have seen that video before but I don't remember exactly what the purpose was or if it was even accurate.

From my past experience, I was always told that the openers are designed so that you cannot bypass the sensors in any way or the opener will not work. This is so that the safety feature cannot be bypassed, avoiding severe injury if the door were to crush a person or pet.

I would have to do some research to see if you really can bypass the sensors.

From what I do know, the tests that you have done prior to this video show that your logic board is good and that the sensors or wiring are the problem. I would stick with that for now. In addition the new sensors and wiring are not going to cost as much as a new logic board. A new logic board averages around $70.
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Customer: replied 4 years ago.
Just want to share the result: tried with brand new pair of sensors (and wires), the problem did not get resolved. Finally got online ordered new logic board yesterday (from Garage Intel), put it on and it works like charm.

Thanks bunch for Brian late night responses.

Bill, that is very interesting. Everything was saying that the board was good and the sensors/ wiring seemed to be the problem. I don't get it but at least you fixed it. Congratulations and have a great day.