In most air-conditioning systems, the condenser unit is located outside the house and is prone to accumulate dirt and debris from trees, lawn mowing, and airborne dust. The condenser has a fan that moves air across the condenser coil. You must clean the coil on the intake side, so, before you turn off the power to the air conditioner, check to see which direction the air moves across the coils. Here's how to clean the condenser:
Step 1: Cut down any grass, weeds, or vines that have grown around condenser unit; they could be obstructing airflow.
Step 2: Clean condenser with commercial coil cleaner, available at refrigerator supply stores. Instructions for use are included. Flush coil clean (do not use hose); let dry.
Step 3: Clean fins with soft brush to remove accumulated dirt. You may have to remove protective grille to reach them. Do not clean fins with garden hose, as water could turn dirt into mud and compact it between fins. Clean fins very carefully: They're made of light-gauge aluminum and are easily damaged. If fins are bent, straighten them with fin comb, sold at most appliance parts stores. A fin comb is designed to slide into spaces between fins. Use it carefully to avoid damaging fins.
Step 4: Check concrete pad on which condenser rests to make sure it's level. Set carpenters' level front to back and side to side on top of unit. If pad has settled, lift pad with pry bar or piece of 2-by-4, then force gravel or rocks under concrete to level it.
During the fall and winter, outside condenser units should be protected from the elements to prevent leaf blockage and ice damage. Cover the condenser unit with a commercial condenser cover made to fit the shape of the unit or use heavy plastic sheeting secured with sturdy cord.