liftmaster Chamberlain Garage Door Opener Transmitter 300MC - Answered Questions & Fixed issues

29 years is along run on an opener. Personally I would replace it and not spend any money trying to repair it. You can try and find a control panel, or buy a new opener for $200.00 at HD. you can leave track in place replace rollers from new opener box.

Sounds like loose connections. Unplug, remove the cover and be sure all connections are tight and secure. While doing this be sure there are no burnt connections or burns on the PCB. Replace cover, plug in and it should be OK.

Yes, follow the directions with your liftmaster, that should solve the problem.

It is probably the lubrication in the rollers. You should lubricate them and make a small adjustment to the torque sensor. When it gets cold the lub gets stiff. The torque sensor will detect this and open the door, a safe position.

https://www.youtube.com/watch?v=Izqj8I_BjHA

When you say sensors, are you talking about the photo-eye that checks if obstruction is in path of garage door?

1) You can buy sensors for $20-30. They seem generic

2) The new openers may be set up so by-pass is not an option.
Solution: In that case, you can move sensors above the garage door and put them face to face to see if that helps.

3) The way the sensors work is this. One side produces beam of light. Other side receives light. The receiver keeps a circuit closed at all times when light is received. If no light, then the circuit opens up and an electronic part interprets the lack of signal and turns off opener.

Solution: one side produces light. It does not have a switch. The other side has the switch. You can disconnect (or cut) a wire see which side has the light. The other side has the switch ... cut the 2 wires on the side with a switch, cap them off, and then see if opener works. Next twist the 2 wires together and see if opener works.

4) Fall-back position: Mark your wires and you can put it back the way it was.

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Something could be blocking the electric eye.they are down at ground level on both sides of the door

Try reprograming the opener to each remote, if this doesn't work then the command/radio module in the opener is damaged and needs to be replaced. Hopefully you can find one or you will have to replace the whole garage door opener. Good luck.

batteries in remote maybe?

Try posting in the correct forum for better results

hi check that the door is free from stifness

http://support.liftmaster.com/articles/How_To/LiftMaster-receiver-and-remote-compatibility-1484145638635 I don't believe a universal remote will work. Here is a link to compatibility

It will only take a 4 digit program code. After you program the code, and then enter that code to open the door, hit an additional number on the keypad. Some need the additional digit to act like an 'enter' key.

Disconnect power to the opener! Then, with a dental tool or small screwdriver scrape off any corrosion etc from the contact in the center of the socket. Also note if it is lying flat against the bottom of the socket. If so, gently lift the center so it has some spring retention and rises up off the flat bottom of the socket.

Check alignment of the obstruction sensors .... they shoot a light beam across the doorway about 6 inches above the floor. One is mounted on each side of the door track near the floor.

This sounds like a similar problem that I had. The circuit board on the garage door motor has a capacitor that goes bad and this prevents the remotes from working. You can either buy a replacement circuit board online (for around $80 if I remember) or if you can solder, simply replace the capacitor for a few dollars. I answered a similar question on this site before after I went through the process. There are more details there. The capacitor in question was close to a heat producing component and over time it cooks.

Try connecting transformer to your other 115 volt line

Your answer is in the last line, unless you have those lights, the opener assumes something is in the way. Make sure you have the green one pointing in the direction of the local sunsets as this is also a problem certain days of the year.

this is likely a force setting issue, with all the humidity the door might be getting more stiff, on the back or side of the unit there should be a screw it adjust, or you can reference the manual, but before doing so you should release the door from the opener (handle on the trolley) and check to see just how stiff the door is, if the spring has broken you will have to get a door guy to fix it.