Limit Switches and Travel Settings

An opener has no idea where the door is. It knows how far it has turned since it started, and the limits are the numbers that turn that into a position. Both settings get checked on every visit, since Orange County Garage Door Tune Up, CA ageducate sees a great many replaced parts in Orange County that were replacing a symptom of a limit that had drifted a quarter turn out on a perfectly healthy garage door.

What the Limits Are

The up limit tells the machine where fully open is. The down limit tells it where the floor is. On older units they are screws driving a threaded rod against a pair of contacts, and on newer ones they are learned positions held in memory. Either way they are a stored guess that can go stale.

When the Down Limit Is Too Far

The door reaches the floor and the drive keeps going. The rail flexes, the top section is pushed down against a door that has already stopped, and the force setting sees resistance and reverses. A door that closes and then immediately opens again is far more often this than a broken safety sensor, and it is a two minute adjustment.

When the Down Limit Is Too Short

The door stops with a gap at the threshold, letting in water, light and everything that walks. People commonly answer this by turning the force setting up, which does nothing, or by fitting a fatter bottom seal, which hides it. The gap belongs to the limit switch.

Up Limit Faults

Set too far and the rear roller runs into the stop bolt at the end of the horizontal track, which bangs and eventually bends something. Set too short and the door parks low enough to catch a tall vehicle. The right position leaves the door just clear of the opening with the wheels well short of the rail end.

Why They Drift

Vibration on a screw type limit, a slipping trolley, a chain drive that has stretched, and any work that changed the door height such as new weather seal at the bottom or a settled floor. Nothing has failed in these cases. The stored position is simply no longer where the floor is.

Setting Them Safely

Adjust in small increments, a quarter turn or one press at a time, and test reversal after every change. The down limit is set with the door lightly touching the floor rather than pressed into it, and the timber test is repeated afterward, since altering travel changes what the force setting sees.