If your air conditioner is losing heat, then the problem may be a clogged condensate drain line. If you confirm that clogging is the issue, then you should clean the line promptly to increase your unit's efficiency. Cleaning it will also prevent further problems such as mold growth.  Here are four methods to employ for the cleaning:

Drain Cleaning Brush

The first step is to clear away the visible debris. For this, you need a bristle drain cleaning brush that can sweep away the bigger particles. If the drain is really clogged, then a visual inspection of the condensate drain will usually yield crud that the brush can remove. Be gentle while using the brush so that you don't damage any of the pipes.

Drain Snake

A drain snake is another option for getting rid of big dirt particles. You don't need a complicated tool for this; just a flexible plastic tube can do the job perfectly. Insert the tube at the trap vent opening and work it through the trap. Again, you want to work gently so as not to damage any of the pipe connections; such damages usually lead to fluid leakages. If you prefer, you can attach a small brush at the end of the snake to sweep away the debris.

Portable Pump

Did you know that you can also use a manual vacuum pump to clear a clogged condensate drain? For this, you just need a portable pump and a suitable inlet adapter. Connect one end of the adapter to the pump and the other end to the opening of the drain. Next, connect the pump outlet to a suitable reservoir (such as a bucket) for the expected waste. There are several brands of portable pumps that you can use for this purpose, and most of them work well enough.

Carbon Dioxide (CO2) Cartridge

The fourth option is to use a CO2 cartridge to blast through the offending dirt. For this, you need to buy a CO2 cartridge canister (get one from your local heating equipment store of online). Most of the cartridges come with different adapter sizes to fit different drainage types.

Once that is done, connect the canister to the condensate drain inlet and plug the vent with an expandable rubber. You can get the rubber from a heating equipment store too. Next, insert the supplied cartridge into the canister and screw on the cap tightly. This will puncture the cartridge and cause the pressurized carbon dioxide to flow through the line and clear the obstruction.

Some of these drain cleaning methods are more involved than others. You can always hire a professional air conditioning repair technician to clean the drain for you. In fact, that is what you should do if you do not know your way around the unit.