Upper Limit keeps changing...

[jayw]

Chamberlain 459950, I set the upper limit, but each time I open the garage, it opens an extra inch or so. After about 5 opens, it hits the stopper. The lower limit remains perfect each time.
I'm guessing this is a circuit issue, but not sure. Has anyone ever seen this? Other than the upper limit, the unit runs perfectly and has for about 3 years.

[HayZee518]

if the limits operate off a cam travelling on a lead screw, contacting two switches, I'd look for some slop in the cam or the switch if its movable.

[TJR]

The open/close limits on that model is controlled electronic by the rpm sensor.
1. when you set the open/close limit you have to set the force setting too.
2. the rpm sensor module can get "loose", make sure it is seated correctly.
3. logic board failure.
and as a diy opener
4. if the cap over the sprocket is NOT installed the belt can skip.
check the balance of the door and check the lock ring on the belt adjuster has been engaged.