A room can only contain a finite amount of air when the windows are closed. So for an air conditioner to direct chilled air into the space, it needs to simultaneously extract warm air. This warm air is absorbed by the unit's evaporator coils, after which it's moved through the unit to be expelled outside. If your evaporator coils encounter problems, your unit simply won't be able to cool the room with any efficiency. How do you know when such a problem is developing?
How Evaporator Coils Work
Fortunately, many evaporator coil problems are minor and are simply down to a lack of regular maintenance for your unit. The evaporator coils use a liquid refrigerant, which extracts warm air from your living space. The moisture in this warm air condenses as water, which is then vaporised (evaporated) by the coils and makes its way into the unit's drainage pan. The refrigerant (which has been warmed by the process) continues travelling through the unit, expelling warm air via the outdoor component of your AC, before cycling back and repeating the process. This process becomes interrupted when the evaporator coils are dirty.
Dirty evaporator coils will struggle to evaporate anything much. Moisture that ordinarily would be directed to the unit's drainage pan becomes trapped, and may even freeze inside the unit, further hampering its efficiency. However, before the internal sections of your air conditioner begin to freeze, you're likely to notice a general reduction in its efficiency. What does this feel like?
A Struggling Unit
It may seem like something is wrong with your unit's thermostat. Although you've set the desired temperature, it can feel like the results don't reach this level. The unit will struggle to reach your preferred temperature, and the room simply won't feel as cold as it should. Additionally, your air conditioner will need to run longer as it tries (and fails) to reach the specified temperature. To achieve and maintain temperature, an AC unit should run itself for approximately 15 minutes, around two to three times each hour. If it seems to be running for extended periods of time, it may be a sign that your evaporator coils are causing trouble.
Act quickly as soon as you begin to suspect that your unit's evaporator coils need attention. Professional air conditioning maintenance is the easiest way to handle the problem. Ideally, it will be as simple as cleaning the dirty coils (and scheduling periodic maintenance to make sure it doesn't happen again).
For more info about air conditioning maintenance, contact a local company.