Question about liftmaster Chamberlain Garage Door Opener Transmitter 300MC

1 Answer

I have a liftmaster garage door that doesn't work. When I hit the button it clicks and the motor spins maybe two turns. All my safety sensors are lit. I know this isn't the problem. However after further investigating the learn light is blinking 5 times, which says the motor is overheated or the rpm sensor is bad. I took the cover off the opener. It looks like the pastic spline screw (middle screw between the up and down adjustment screws left side of case)(gray wire) has overshot the up limit switch (yellow wire). It seems like it notices that it's hit the limit, but it doesn't want to reverse direction. So, I disconnected the RPM sensor. In doing this the garage door actually continued without stopping but still in the up direction. Any ideas if this is really the rpm sensor or the logic board or what?

Posted by on

1 Answer

  • Level 1:

    An expert who has achieved level 1.

    All-Star:

    An expert that got 10 achievements.

    MVP:

    An expert that got 5 achievements.

    Vice President:

    An expert whose answer got voted for 100 times.

  • Contributor
  • 504 Answers

YOU COULD TRY

RECONNECT THE RPM SENSOR, UNPLUG THE UNIT. TURN THE MOTOR BY HAND (DOWN DIRRECTION) TO CLEAR THE LIMIT SWITCH.

PLUG THE UNIT IN IF. IT STILL OVERSHOOTS THE LIMIT IT COULD BE A BAD LIMIT SWITCH. IF THE SWITCH TESTS GOOD FOR CONTINUITY REPLACE THE BOARD.

HOPE THIS HELPS

Posted on Jun 05, 2010

1 Suggested Answer

6ya6ya
  • 2 Answers

SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

Hi,
a 6ya expert can help you resolve that issue over the phone in a minute or two.
best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.
the service is completely free and covers almost anything you can think of (from cars to computers, handyman, and even drones).
click here to download the app (for users in the US for now) and get all the help you need.
goodluck!

Posted on Jan 02, 2017

Add Your Answer

Uploading: 0%

my-video-file.mp4

Complete. Click "Add" to insert your video. Add

×

Loading...
Loading...

Related Questions:

1 Answer

Auto garage door opens will not close not the sensors


Look at the back of the motor unit and see if that little light is flashing a code. Post the code.

Aug 13, 2012 | Sears Craftsman LiftMaster Chamberlain...

3 Answers

The garage Remote control was working normally at first then for now reason now it just opens the garage door but doesn't close it. I checked the side sensors they look OK & clear, and I...


It could be the garage door motor that is acting up. Try closing it with the button in the garage. If that's not the case, you may need a different garage door opener.

Jun 06, 2011 | liftmaster Garage Door 1/2 Hp

2 Answers

I have a chamberlain liftmaster professional Formula 1 Garage door opener that has been working for 5 years. Now will not go down unless you hold the main button. Sensors blink when it hits within 3...


Anytime the main light flashes 10 times and the door reverses to the open position it is a door sensor problem. They each have a small light that should be lit, both should be the same brightness and not flickering ever so slightly. If not tweak them a bit. If both lights will not come on you have bad sensors.

Sep 27, 2010 | Sears Craftsman LiftMaster Chamberlain...

2 Answers

Liftmaster Garage Door Won't Close


Sounds like maybe the door traveled too far and the trolley has jammed against the bolt just in front of the motor. If so, loosen the chain enough to take the tension off the chain and then run the opener until the door closes. While the door is closed locate the 'up limit' control on the side of the motor unit and turn it 2 full turns in the opposite direction of the arrow printed on the cover. Tighten the chain.

May 27, 2010 | Sears Craftsman LiftMaster Chamberlain...

1 Answer

Liftmaster Chamberlain Garage Door Opener Transmitter 300MC: Light keeps on flashing on the motor...


how many flashes
1-safety sensor wire broken
2-safety senor wire shorted or reversed
3-door control or wire short
4-safety sensors mis aligned
5-motor overheated or bad RPM sensor
6-circut failure, bad logic board

May 17, 2010 | liftmaster Chamberlain Garage Door Opener...

4 Answers

Craftsman Garage Opener Clicks only and LED blinking 5 times


Just fixed this problem tonight. Had the 5 blink/flash thing. Opened it up and saw that the motor wasn't spinning so it wasn't a bad rpm sensor. Jumped the red to black and then the blue to black to verify motor worked. At that point assumed it was the logic board not telling the motor to start, but I could hear the click of the relay. Pulled the logic board out and noticed a solder joint that had failed directly behind one of the relays. Resoldered that joint and the garage door opener worked again like a dream. Hope that helps someone else.

Feb 28, 2009 | Building Materials

3 Answers

Craftsman Garage Opener Clicks only and LED blinking 5 times


first off, hitting extra button on remote would not do anything. Is door up or down/ where is trolley that attaches to chain, by door or motor. Is is jamned against a bolt. Try a paper clip and jump from white to read terminal. Does it work. Does light bulb blink 10 times. I ignore the diagnostic lights and go by symptons. Give more info.

Dec 29, 2008 | Sears Craftsman LiftMaster Chamberlain...

1 Answer

Not working


IT MAY BE AGAINST THE TRAVEL LIMITER BOLT.

IF IT IS YOU WILL NEED TO UNPLUG THE UNIT REMOVE THE COVER AND TURN THE MOTOR BY HAND TO BACK OFF THE PRESSURE.

MAKE SURE YOU GO PAST THE LIMIT SWITCH.
ADJUST THE LIMIT SO TH DOOR DOES NOT HIT THE BOLT.

HOPE THIS HELPS

Sep 07, 2008 | Sears Craftsman LiftMaster Chamberlain...

1 Answer

Red supmart button


The safety interlock sensor is blocked or not working - those are the sensors at the bottom of the door that check for blockages.

Jul 21, 2008 | Sears Craftsman LiftMaster Chamberlain...

1 Answer

Opener has power but does not open.


The surge probably knocked out one (or more) of the safety sensors.
There may also be a fault on any control board involved.

Each of these components (including the main drive motor) will need checking that they are still working correctly.

Only by a process of elimination will you find the fault. This can be done by checking the outputs of each sensor in turn, and testing operation.

Make sure the system is isolated before atempting this, and ensure a safe working practice is followed.
It's not worth losing fingers over!

Once the fault is found, do not use untill a replacement is fitted.

Hope this helps.

May 20, 2008 | Sears Craftsman LiftMaster Chamberlain...

Not finding what you are looking for?
liftmaster Chamberlain Garage Door Opener Transmitter 300MC Logo

1,031 people viewed this question

Ask a Question

Usually answered in minutes!

Top liftmaster Electrical Supplies Experts

Vince Heuser

Level 2 Expert

118 Answers

tamska1102

Level 1 Expert

28 Answers

ray gallant

Level 3 Expert

41433 Answers

Are you a liftmaster Electrical Supply Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides

Loading...