First, let’s name the basic components of your central air system. The unit that’s inside your house is called the blower or evaporator. Outside the house is the condenser and compressor unit. This is a large metal box with a fan inside that’s typically located by the garage. It’s kept outside mostly because it’s loud and generates a lot of heat.
Replace the filter
The filter in your blower motor should be replaced twice a year or whenever it’s clogged with dust. A clogged filter slows down airflow, which can create ice on the coils and shut down the unit. Check it once a month throughout the season to make sure it’s clean. Replacing a dirty filter with a clean one can use 5% to 15% less energy (1).
Clean the condenser
The condenser unit sits outside and has been sucking up debris and dirt for several months. All that junk will keep the system from working efficiently. Before doing anything to the condenser, shut off power on the disconnect box near the unit and at the main service panel in your house. Allow 30 minutes for electrical charges to dissipate.
Remove the grills from the unit. Don’t tug any wires. Clean the coils using a refrigerator coil brush or a soft brush on a vacuum. Be careful not to damage the coils or bend the fins. For any stubborn debris, use a commercial coil cleaner.
If you can, disconnect the fan and gently pull it out. Scrub it down with a garden hose and rag. If the fan motor has oil parts, lubricate it with WD-40.
Scoop out leaves and other debris from the condenser box. If there is a drain, make sure it’s clear. Mop up excess water. Reassemble everything and tighten any loose bolts. Allow the unit to dry thoroughly before turning the power back on. Turn the thermostat off before flipping on the main power switches.
Remove anything within a foot of the condenser that could obstruct airflow such as weeds, vines, shrubs, low-hanging branches, and wood piles
Check pipes and vents
The coolant pipes connect the condenser box to the blower inside the house. They are covered with foam insulation to prevent energy loss. If you see areas where the foam is frayed or missing, replace it with either foam pipe covers or foam insulation tape.
Make sure no rugs or furniture are blocking the vents in your house. Open the vents to check for anything inside that could cause problems. If you find mold, contact a qualified professional that cleans ducts.
It’s never a bad idea to call the professionals anyway to service your unit at the start of the season. They’ll make sure everything is working at its maximum efficiency and troubleshoot any future problems.