You'll quickly realize you air conditioner is the mediator that maintains peace and civility within the walls of your home. Now Imagine it broken, and imagine the HVAC guy is really busy this week because the heat wave that finally brought down your unit has been making mischief all over town. It doesn't have to be that way. you can get ahead of the curve, and get a few more years out of your most important appliance with some simple maintenance.
Cut the power to the unit. Skip this step and you and the unit might both need repairs. Give the outside unit (also called a condenser) a good scrub. Not a hard scrub, mind you. Those little metal fins are the target, and they're pretty delicate, so be gentle. They're what you might call a heat sink. Your AC unit has a pretty substantial motor in it, and that thing can get pretty hot. Clogged fins don't disperse heat. In fact, they insulate and cost you money in higher electric bills along with repair costs. clean out the debris from the inside while you're at it. You might be surprised what you'll find in an enclosed, protective box that stays warm in the winter. Here's a hint: it's mice.
Spray around the condenser with a bug repellent. Ant's are brilliant in the dumbest ways. There are multiple theories as to why they're attracted to AC condensers, but suffice it to say once one of the little guys gets zapped by the electrical contacts inside, the hive mind sends in wave after wave of brave soldiers to help out their buddy. They all die, but they take your unit down with them.
Now give the inside unit much the same treatment as the outside and you change your filter regularly and you'll have a healthier air conditioner, and as a bonus, maybe a slightly lower electric bill too.