Hi Folks,

We have two liftmaster garage door openers. Both were working fine this morning. Neither experienced any known trauma. Now one is working fine the other seems to have spontaneously become miscalibrated.
The wonky door does not open all the way and when it goes down it hits the ground and goes right back up - to the not fully open position.

If I look at the two units each has a chain, and a metal piece with slot where the door slots in. The spot where you can disengage the door for manual use.

For the working you unit this metal piece stops right by the unit. But for the wonky one the metal piece stops more than a foot short. It is as if the unit had a brain fart and now has the wrong stopping/starting point.

I can find no way to move the chain so that the metal piece with the slot can be moved to the same position as the one that is working correctly.

I'll start googling for the installation manual in the morning but just hoping someone says: Oh yea, I know how to fix that.

TIA

Take a look at the springs on the door and for obstructions in the track. If it's not one of those with issues, try adjusting the opener.

Try holding the button down until the door motor shuts off. Sometimes that resets it .

Like 95flhr said, check the springs. I had a similar issue, and it turned out the wire that attaches to the torsion spring had come off its pulley. Re-attaching required me to completely unwind the torsion spring. But, I am glad I did, as the original installer never adjusted it properly, and once i re-did it, the garage door works better than when it was new.

If you do need to work with the torsion spring (assuming yours is that type), be careful, as it has a lot of energy and can cause serious injury. I learned how to do mine from Youtube videos.

Sounds like the limit switches or the component that triggers them is out of wack.

quote:

Sounds like the limit switches or the component that triggers them is out of wack.

That's what it sounds like to me as well. It's closing, but touching the ground before it thinks it's where the door needs to be. This is activating the safety that reverses the door.

Don't know how it works on your type of opener. I have liftmaster commercial openers. There's a brass shaft with two contacts, one at either end. Nylon nuts on that shaft are turned to adjust the start/stop points.

Thanks everyone. I looked at the spring and it the wonky one and the one that is working correctly seem exactly the same.

I'll take a look at the limit switches.

You didn't mention if your unit has the laser-eye thing obstruction-detector.

Mine has the laser-eye DBAL looking boxes which face each other. I guess they emit IR beams, which if not aligned to each other's sensors, will autmatically cause the door to stay in the up position (goes down, even all the way down, then bounces back up).

(the kid who got killed before these were invented? I knew him and went to school with him--very sad story).

I was sweeping one day and bumped the laser eye just a little bit. My door did the same thing yours is doing. I had to cant the sensors back into alignment and that fixed it.

Part of a former job included installing and repairing garage doors...

If the problem is not immediately obvious, no broken springs or cables hanging down etc, the first thing to do is to disconnect the door from the opener and check for proper function manually. Open and shut it a couple times to see if it operates properly by hand.

Thanks for all the suggestions. The door goes up and down find.

Here are some pics in case it helps.

This is the bad door. See how far back the metal plate (that connects the chain to the door ) is relative to the unit.





This is the good door. Metal plate back by the unit.



And this shows how far the door is from being fully up when the unit stops.





You can see how far down the door on the left is in the fully up position. And it looks to me like that distance is similar to the distance that the metal plate is back in relation to the door that works correctly.

It just spontaneously started to do this yesterday.

Pull red handle to release latch, manually lower door to closed position. Re-engage the latch. Open door with opener. After that, I got nothing....

quote:

Originally posted by TXJIM:
Pull red handle to release latch, manually lower door to closed position. Re-engage the latch. Open door with opener. After that, I got nothing....

Good idea, but we already tried that. It just goes back to that same set point.

I had the same thing happen recently on the same opener, or at least a very similar one.

I even have pictures of the fix, but can't get to them at the moment.

The problem is with the limit switch assembly. They are plastic gears and they just wear out. They sell a whole new assembly for like $30 that I ended up buying and replacing to resolve the issue.

I'll get you some pictures in a few hours if you need, but if you take the cover off you might see the issue. There are a set of gears that move flags in and out of sensors and I'll bet one of them is slipping in one direction. I temporarily fixed it by using some electrical tape on the gear teeth to help them "mesh". While I waited on the part to arrive.

this is most likely what you need.

Guess it wasn't even $30
http://store.garagedoorsupplyc...D0xNMCFQeewAod2K8FMg

I also bought the other gear that meshes with the gear on this one just to be safe I replaced them both.

Thanks ube. I'll take a look at lunch time.

Limit switch needs resetting, to set the limit(s) on fully open and fully closed.
I just installed a door a few months ago, and became intimately familiar with limit switches, lol.
Is a PDF of the unit's installation guide available from the manufacturer online? If so, get it and find out how to set the limit switches.

quote:

Originally posted by VictimNoMore:
Limit switch needs resetting, to set the limit(s) on fully open and fully closed.
I just installed a door a few months ago, and became intimately familiar with limit switches, lol.
Is a PDF of the unit's installation guide available from the manufacturer online? If so, get it and find out how to set the limit switches.

I downloaded the PDF and while a Limit Switch is listed in the parts list there is nothing about how to use/change it's settings.

Haven't had a chance to open it up yet. Work has been busy.

 
Whatever you do, don't mess with the torsion spring with only a screwdriver. Use a solid
1/2 bar of solid steel or thick pipe. Better even yet is a 3/4" or 5/8" bar that has been turned down to 1/2" for contact with the spring adjuster. Those springs can kill you.
 

Chance,

Sorry for the delay, I couldn't find the picture last night but it was right where I thought it was this morning...

In the picture the red circle is the gear that wore out on mine. The blue stuff is electrical tape I wrapped on one of the gears to give some friction until I got my new limit switch assembly.

The orange circles are the adjustments for the limit switches which have contacts on them. One for up, one for down. The shaft in the middle is moved as the garage door moves, and also has a contact on it. All of them have wires attached that lead back to a PC board. When it makes contact at either end it stops.

What happened with mine is that the gear would mesh one way, but not the other, and the more I moved it back and forth the more out of whack it got until the whole thing was jammed. I then had to undo the chain to relieve the tension and redo the range of motion. If you haven't got it jammed already you can probably just do the tape trick and it will be OK until you get a replacement assembly.



If you have specific questions or what not my email is in my profile.

If you're having the same problem I had you'll see what it's doing once you take the cover off.

One of my openers has two screw adjustments on it. One for up and the other for down for that adjustment. But, if your plastic gear is worn out, that will not help, like the previous poster stated.