Your home has a long, hot day ahead of it, so it's time to turn on the air conditioner. But once you turn it on, you get nothing but warm air out of it no matter how low you turn down the thermostat. There are plenty of issues that can prevent your air conditioner from performing as it should, but the following four issues may not be as common as, say, a dirty air filter or a refrigerant leak.

Blocked Coils

The evaporator and condenser coils play central roles when it comes to your air conditioning. The evaporator coil uses refrigerant to absorb the heat in the air that passes between its coil fins. This latent heat is then moved to the condenser coil, where it's then released into the outdoors. Dirt and debris buildup can block this heat transfer process, effectively leaving that warm air stranded inside your home.

For your condenser coil, it's a good idea to check it for any buildup of leaves, dirt and other yard debris. In most cases, a simple rinse from your garden hose should knock off most of the dirt and debris. You should also make sure the area immediately around the bottom of the condenser is free of any potential blockages, including shrubbery and fencing.

For your evaporator coil, a simple cleaning with a soft-bristle brush, mild dish detergent and warm water should take care of most dirt and debris buildup. Remember to scrub gently when cleaning the evaporator coil, as you don't want to damage any of the fragile aluminum fins.

Leaky Ductwork

If you have a central air conditioner, then chances are your home has an extensive network of ducts that deliver cool air to various parts of your home. Any type of leak along the ductwork could let cool air escape into the crawlspace or between walls, preventing it from reaching the areas that need it most.

It's a good idea to have your HVAC technician conduct a thorough inspection of your ductwork. Your technician will be able to locate these leaks and make the proper repairs necessary to restore your air conditioning system's performance.

An Aging A/C Unit

Air conditioners are capable of lasting for quite a while, but they're not designed to last forever. According to the U.S. Department of Energy, a typical air conditioning system may last for 15 to 20 years before it needs replacing. Some units are able to last for much longer, but that often requires investing hundreds or even thousands of dollars in constant maintenance.

The older an air conditioner gets, the less likely it'll be able to maintain the same performance and efficiently it had when it was brand-new. You can chalk that up to aging technologies and overall wear and tear getting the best of your air conditioner. Newer air conditioners often have better efficiency and performance than their older predecessors, so it's usually a good idea to invest in a new unit if your current one is pushing past the 15-year mark.

Undersized A/C Unit

Deliberately installing an undersized air conditioner might seem like a good idea at first. After all, a smaller air conditioner should use less energy than a bigger unit, or so the thinking goes. In reality, an undersized air conditioner will constantly struggle to reach your thermostat temperature set point, resulting in more energy used than with a properly sized air conditioner and more wear and tear on A/C components.

Instead of choosing an undersized air conditioner in hopes of conserving energy, you're better off buying a properly sized air conditioner that not only offers better performance, but also less energy consumption.