My Air Conditioner Smells Bad When Running for a While

Filter

• If your air conditioner releases an unpleasant odor, change or clean the air conditioner filter. Some air conditioner units feature a washable reusable filter while others require the filter to be replaced. If the filter is reusable, open the air conditioner grille and remove it from the unit. Use warm water and your fingers to remove dirt, grime and other buildup from the filter completely. After the filter is clean, dab both sides of it with a towel or lay the filter out until it's dry. Reinsert it into the air conditioner, close the grille and turn the unit on.

Existing Air

• When the air conditioner is in venting mode, air from outside might be circulating through the air conditioner and into the room. Turn the unit off, and smell the air outside of the air conditioner. If the air is unpleasant, close the air conditioner vent and switch the unit to the "Fan" or "Cool" mode. Inspect the room for items that might emit an unpleasant odor, such as forgotten food. Check the area especially around the air conditioner. Remove the offending materials from the room, and switch on the air conditioner's "Clean" feature, if it has one, to clean the air.

Drain Pan

• Some units, such as portable air conditioners, feature an internal drain pan to catch moisture from the "Cool" or "Dry" cycle. These cycles remove moisture from the air and allow it to collect within the drain pan for later disposal. If the collected liquid isn't drained and sits inside the air conditioner for extended periods, the liquid might develop a foul odor. Empty the drain pan by carrying the unit to a drainage area, removing the drainpipe cap and plunger and allowing the unit to drain completely. Replace the plunger and cap, and return the unit to its position.

Compressor

• There might be electrical damage or internal damage to the compressor if the air conditioner emits a burning smell. Turn the unit off immediately, and unplug it to be safe. Consult an electrician or the air conditioner manufacturer for service or further instruction.