On a hot day, you want to turn on your air conditioner and enjoy the cool, clean air. Nothing can ruin that feeling faster than a bad smell emanating from the air conditioner. A musty smell usually indicates that mildew or mould is growing somewhere in the unit. If you are getting a musty smell, you will need to clean and disinfect your air conditioner before turning it on again.
Take the front grill off the air conditioner, and remove the filter. If it's a disposable filter, simply replace it. If it's reusable, then you'll need to clean it by laying it flat in a sink or tub, sprinkling the surface with washing powder, and filling the sink with about an inch of hot water.
Let the filter soak for 15 minutes. Remove it from the soapy water, rinse it thoroughly, and hang it to dry. The filter must be completely dry before you put it back in the air conditioner.
Follow the manufacturer's instructions to clean the inside of the air conditioner. Unplug the unit, and use a bristled brush to remove dust and dirt from the coils and evaporator.
Spray a solution of white vinegar and water on the coils, fins, and other surfaces. Use a clean cloth to wipe them, being careful not to bend the fins. After the vinegar smell dissipates, most odours should be eliminated.
Drain any hoses or tubes according to the manufacturer's instructions. If you can take them off, do so carefully, and wash them out with soap and water. If they smell musty, rinse them in straight white vinegar to disinfect them.
Allow the hoses to dry completely before reattaching them to the air conditioner.
Run the air conditioner for several minutes after you reassemble it. The musty smell might not go away immediately, but it should subside after the unit runs for a few minutes. If you can't stand the smell, leave the room for a few minutes while the air conditioner runs.