Evaporator Coil Repair

The evaporator coil sits inside your air handler or furnace, positioned in the path of airflow from your ductwork. Cold, low-pressure liquid refrigerant enters the coil through a metering device, typically a thermostatic expansion valve or fixed orifice. As warm indoor air from your return ducts passes over the coil fins, the refrigerant absorbs heat and evaporates into a gas. This is the fundamental process that removes heat from your home. The cooled air continues through the supply ducts to your living spaces, while the now-gaseous refrigerant travels to the compressor in the outdoor unit to release the absorbed heat.

The evaporator coil also plays a critical role in dehumidification. As warm, humid air contacts the cold coil surface, moisture condenses out of the air and drips into the condensate drain pan below the coil. This is why your AC reduces humidity as well as temperature. A properly functioning evaporator coil should produce a temperature drop of 15 to 22 degrees Fahrenheit across the coil, measured as the difference between the return air temperature and the supply air temperature. If your temperature drop is significantly outside this range, the coil may have a problem that needs attention.

Frozen coil repair begins with identifying the root cause. We start by turning off the system and allowing the ice to melt, which can take several hours. Attempting to scrape or chip ice from the coil can damage the delicate aluminum fins. Once the coil is thawed, we check the air filter, inspect the ductwork for obstructions, test blower motor operation, and measure refrigerant charge. If the cause is a dirty filter, we replace it and verify normal operation. If the cause is low refrigerant, we perform leak detection to find and repair the leak before recharging the system. For evaporator coil leaks, repair options depend on the location and number of leaks.

A single leak at a brazed joint can often be repaired by re-brazing the connection. Multiple leaks from formicary corrosion typically mean the coil has widespread damage that will continue to produce new leaks even after individual repairs. In these cases, coil replacement is the more reliable and cost-effective long-term solution. Coil cleaning is performed during our annual maintenance service. We use specialized coil cleaning solutions that dissolve dirt and biological growth without damaging the aluminum fins. We rinse the coil, clean the condensate drain pan, and flush the drain line to prevent clogs.

For heavily soiled coils, we may need to remove the coil from the air handler for thorough cleaning.

The most effective way to prevent evaporator coil problems is consistent air filter replacement. We recommend checking your filter monthly and replacing it every 1 to 3 months depending on filter type, pets, and indoor air quality. A clean filter keeps the airflow adequate and prevents dirt from reaching the coil. Annual professional maintenance includes coil inspection and cleaning that removes buildup before it becomes a problem. We check the condensate drain for clogs that could cause water backup and overflow. We verify proper refrigerant charge, which prevents the freezing cycle that damages coils.

For homes prone to formicary corrosion, we recommend minimizing the use of volatile organic compound-producing products near the air handler return. Sealing the area around the air handler to prevent unconditioned air infiltration also helps by reducing the amount of contaminants that reach the coil. Installing a UV light in the air handler can help prevent biological growth on the coil surface, reducing both odors and the insulating effect of mold and mildew on coil performance.