An air conditioner drain can become clogged over time, even with regular maintenance. This will affect the performance of the air conditioner, and can cause it to overheat, create water damage, and cause the air to just quit all together. If you suspect the drain is clogged, it's a relatively simple fix. Make sure you cut the power to the air conditioner before starting on this project.
Step 1 - Check the Outside Drain Pipe
If you think your air conditioner drain is clogged, you can diagnose this by checking the outside drain pipe. The outdoor drain pipe will be set up right next to the air conditioner. If there is no dampness near this, it's a pretty safe bet that the drain is clogged. Even a small puddle can still signal a problem.
Step 2 - Check the Drain Tray
If the pipe isn't draining as it should, check the drain pan. This is going to be found with the main evaporator unit. If the pan is full of water, then you definitely have a clogged drain. This water is what should be draining outdoors through the drain pipe.
Step 3 - Shop Vacuum
A mini shop vacuum, or a full-size one with a small hose attachment will work for this step. You will want to attach the hose to the drain pipe. If the hose from the vacuum doesn't fit securely you can use duct tape to secure it. Turn on the vacuum and allow it to run a few minutes. Turn it off and check the vacuum. You should see some sludge and grime in the vacuum. You will want to do this several times until the sludge and grime stops flowing in to the vacuum.
Step 4 - Check the Drain Itself
Once the clog has been removed, it's time to make sure it doesn't happen again anytime soon. You should be able to get to the air conditioner drain by removing the PVC cap on top of the drain. From here you can look into the drain with a flashlight. It should be relatively clear at this point since you pulled the clog out with the vacuum. Add a small amount, a tablespoon at most, of bleach to the drain pipe. This will help to clear out any gunk that has accumulated along the inside of the drain pipe.
Step 5 - An Ounce of Prevention
As the saying goes... You should make checking the drain a regular part of your household maintenance. If you've had several problems in the past, try to do this monthly until the problem is gone. After that you can just do this at the beginning of the air conditioning season, and then again at the end of the season.
Step 6 - Regular Services
It's also important to have your air conditioner serviced on schedule to prevent major and costly problems later.