You stand at the door with the opener's manual open and the car out of the way. Before you touch anything, decide what kind of job you are looking at. Some opener upkeep is routine work a homeowner can do with a few basic tools. Other work involves springs under heavy tension, door hardware that carries the full weight of the door, or wiring inside the wall. That work belongs to a trade.
Start with the safety reversal. Put a flat board on the floor in the door's path, close the door, and watch it stop and reverse when it meets the board. Then test the photo eyes. Wave a hand through the beam while the door is closing, and the door should reverse. If either test fails, write down what happened before you change any setting. Force and travel limits are adjustments the manual describes, and if a careful adjustment does not clear the fault, call a trade.
Check the photo eye alignment next. The two small sensors near the bottom of the tracks should face each other. Look for a steady light on each. Wipe the lenses with a dry cloth, then look at the wire clips and the bracket before you assume the sensor is faulty. A blinking light usually points to alignment or a blocked beam, and the manual lists what each light means.
Keep the track clean and clear of debris, and lubricate the moving parts the manual names, typically the rollers and hinges. Do not oil the chain or belt unless the manual tells you to. Tighten bolts you can reach from a step stool, and stop if a bolt strips or a bracket moves. A loose bracket is a reason to call a trade, not a reason to add more force.
Batteries in the wall keypad and remotes are yours to change. So is reprogramming a remote, which the manual walks through in its own sequence. Keep a short note in the manual of the last time you ran the reversal test and what you saw. That note gives a trade a starting point and shows you whether the reversal is slipping over time.
Hand these to a trade: any work on the springs, cables, drums, or the bracket that holds tension, replacing the drive unit or motor, changing the ceiling mounting, and any wiring or outlet work. A reversal test that still fails after the simple checks also goes to a trade. Do not force the door to work around a fault.
Before you call, gather what you checked and what happened. Note the door's behavior, the light patterns, which tests passed, and what you adjusted. A trade can then skip the steps you have already covered. If the opener is still under the seller's or maker's paper, ask whether your own adjustments or an unapproved repair could affect that coverage. The paper will say, and it is worth reading before the visit.
For how long a unit tends to last and how to plan around its age, see the garage door opener page.