Liftmaster 3800 problem

[ThePublisher]

I tried to search for this, but had no luck.

My Liftmaster 3800 will open my garage, but it will not go back down. The motor runs for a second but nothing moves. I can disengage the opener and bring the garage back down manually, then reengage and it will open again. It's not the safety sensors as the overhead light flashes when something is in the way and both lights on the sensors are normal. The manual says its possibly the RPM sensor since the diagnostic light on the unit flashes 5 times.

Any ideas? Thank you in advance.

I love this garage door opener, it's so quiet, fast and minimalistic.

 

[empeg9000]

Did you check your door sensors to make sure they are fully in the terminals on the opener. I was having this same problem recently. The wire was just slightly lose in the connect. I took it out and reinserted it and it starting working fine again.

 

[ThePublisher]

Checked everything and one connection may have been slightly loose, but it's still not working. Thanks for the response.
After checking connections I raised the door again. When trying to lower it, the motor pull itself up even more (flexing my door). I disengaged the motor to release the tension on the door and now the door wont go up or down. The motor starts to engage for about a second and then stops, just making the door jump a small bit.

 

[pattenp]

Need more info.
Is this a new install that doesn't work from the start or an existing install that worked at one time and now doesn't?
With the opener disconnected does the door lift up and down easily by hand?

 

[omr]

i dont have any personal experience with that particular door opener but it sounds like a sensor/micro switch issue , my opener has a sensor to stop the motor when the door is fully open , if that sensor isnt being activated the opener wont know to go down the next time the opener is activated ..

 

[ThePublisher]

Need more info.
Is this a new install that doesn't work from the start or an existing install that worked at one time and now doesn't?
With the opener disconnected does the door lift up and down easily by hand?

This was installed with the house (built in 07) so it has been working fine for years. When disconnected the door does just fine. It takes some umph to lift it and you have to let it down gently with some pretty good help, but it works smoothly.

i dont have any personal experience with that particular door opener but it sounds like a sensor/micro switch issue , my opener has a sensor to stop the motor when the door is fully open , if that sensor isnt being activated the opener wont know to go down the next time the opener is activated ..

This sounds very accurate as to what it is doing. I will check into this.

Thanks, you guys are great!

 

[ThePublisher]

OMR: I think you hit it right on the head. When opening the door I can stop it with a press on the remote, another press (which should make it go back down) makes the door continue on its way up. So it doesn't know to go back down.
Anybody know what this sensor is called so I can figure out where it is and replace?

 

[pattenp]

I believe you're looking at replacing the logic board. Take off the front cover and you'll see one circuit board. There is also another part called the "Absolute encoder", not sure what it does. Both of these are available as replacement parts. The board runs around $60 US and the encoder is about $10 US.

Absolute encoder: http://chamberlain.custhelp.com/app...e-encoder-system-installation-and-programming

See part here: http://www.gatehousesupplies.com/41A6118-Absolute-encoder-p/02-41a6118.htm

 

[ThePublisher]

Thanks pattenp! Great that a community can get together and solve problems to save people time and money.