Automatic garage door openers are prone to a variety of problems, most of which are fairly easy to fix with routine troubleshooting and maintenance. One of the more perplexing issues, though, is when the garage door begins to go up and down by itself, with no help from you. It can seem quite ghostly, having your garage door operate with a mind of its own as you watch wordlessly. It can also be a security problem when it opens to expose your belongings when you aren't home. A garage door that begins to close on its own can also be a safety concern, especially in a home with children.
There are several places you can begin looking for solutions to this strange behavior.
Check With Your Neighbors
In rare instances, it's possible that a nearby neighbor has a garage door opener set to the same wireless code as your opener. This is rare, but it does occasionally happen. It is quite easy to check—just have your neighbor activate his garage door and see if your door begins to move. The solution here is for you to reset your garage opener to a new code—every garage door opener has instructions for how to do this.
Inspect the Control Wiring
A bare spot or a short circuit in the small-gauge wire that leads from the motor unit to the control button in your garage may well cause your garage door to operate all on its own. All that's necessary for this to happen is for a bare spot in the wire to brush up against the metal door track or another part—the electrical impulse will cause the motor unit will be activated. Also, check the wiring between each of the safety sensor eyes at the sides of the door and the motor unit. These are low-voltage wires, so you don't have to worry about shutting off the power to check them. Look for damaged insulation, bare strands of wire, or even a nail or staple piercing the wire. When this happens, it's often down near the sensor eyes themselves, where mice can sometimes chew through the insulation, or where the wires are damaged by a broom or shovel.
It's a fairly easy matter to replace these small wires. This kind of small-gauge bell wire can be purchased at any home improvement center or hardware store.
Check the Control Buttons
If the wires appear to be in good shape, next look at the control button mounted near your side entry door. If it is old or dirty, the button may stick. The symptom of this is a garage door that is in constant motion, opening fully then immediately descending, only to start the same cycle again. There may also be loose wire connections inside the button housing itself. As these wires short against the housing, the electrical impulse causes the door opener to activate.
Replacing a malfunctioning control button is another very easy fix.
Circuit Board Issues?
When a garage door descends on command, but then immediately reverses itself, the problem is usually with the sensor eyes along the side tracks or with wheels binding in the tracks. But when the door begins to descend all on its own, the problem may point to the opener's logic board or the circuitry inside the motor unit itself. Garage door technicians have reported instances of this, sometimes accompanied by the opener's lights flashing, much in the same way that some door openers flash when the sensor eyes detect an obstacle.
Theoretically, it might be possible to repair circuit board problems—the problem could be a matter of resoldering a loose connection. This isn't a project for most casual DIYers, although it might be worth the exploration if the alternative is to replace the garage door opener anyway. But having a service technician come out to attempt such a repair will probably cost you as much—or more—than replacing the garage door opener entirely.
Installing a new opener is a very doable project for any moderately handy person. Given that the problems with your opener pose real safety and security risks, a new opener makes a lot of sense if you can't stop its mysterious behavior soon.