My air conditioning stop cooling after around 15 minutes. What could be the problem? What could I do?

I had a similar problem with mine, many years ago, and it turned out to be a water drainage problem.

Over a period of years, the water drainage tube gets impacted with a kind of sludge that looks like mud, and is caused by impurities in the water that runs out from the unit. It builds up, and the water can no longer seep out, so the unit essentially shuts itself down, by halting the cooling process.

If you still have the owner’s manual for the unit, it may describe how to clean and service the exhaust ports and drainage tubes. If not, then you might need to call a service company that specializes in repairing those units, assuming that it can be repaired.

Your other option, of course, is to purchase a replacement (new) unit, as soon as possible, because there is a danger that the unit could overheat and burst into flames.

August 30, 2008, 11:44 AM EDT

One thing that can cause this is build-up of ice on the coils of the AC unit. The coating of ice acts as an insulator that keeps the air passing over the coils from getting as cold as it should. Lots of things can cause this to happen, including low refrigerant level, cool outside temperatures (<65 degrees), dirty filters, or a poorly functioning fan.

To de-ice the coils, set the thermostat to run the fan only, without cooling, and let the fan run for several hours (4–5). This pulls air over the coils and will eventually melt the ice. When you turn the AC back on after this, if it blows cooler than before, then this is likely your problem.

The coils will eventually ice up again until you identify the root cause. Certainly check the filters, but low refrigerant level is a common cause, and you’d have to get it recharged by a technician.

Harp’s answer is much better than mine.

He’s right about what he says.

August 30, 2008, 2:09 PM EDT

you have to get out there with the unit. turn off the AC. take off the top and the sides. power wash the vents and slats with a good garden hose and nozzle. spray clean with hose water “only” around the whole unit. scrub any residue or buildup. even spray down inside fan. it wont hurt. it’s an outside unit that works when the rain falls, so why not? reassemble unit and turn on the AC. immediate results. also, check air filters around furnace and change if needed.