Evaporator coils for a central heating and cooling unit are typically located within the air handler portion of the furnace. The evaporator coils receive liquid refrigerant, which is passed along from the outside condensing unit, and convert the refrigerant back to gas. This conversion causes the coils to become cold. A blower fan cycles air from inside your home across those coils and out your vents to produce the cooling.

Problems with the evaporator coils and the related parts can lead to inefficient cooling or a total lack of cooling. There are a couple of common potential problems that are relatively easy to fix yourself, but might require the help of an AC repair technician.

Inefficient Heating: Frozen or Dirty Coils

Has your cooling system become less efficient suddenly or completely stopped pumping out cool air? One of your first checks should be to see if the evaporator coils are dirty or frozen over.

Turn off all power to the furnace before removing the back cover. The air handler itself might have a separate cover you will need to remove, but after that you should immediately see the coils. Conduct a visual inspection to see if the coils seem dirty or if ice is collecting on the surface.

Dirty or lightly icy coils can be cleaned using a foaming, no-rinse cleanser and gentle strokes with a steel brush. Continue to check the coils every few months to make sure the dirt isn't accumulating again.

If the coils have substantial ice, or if the light icing keeps returning, you might have a refrigerant issue. A refrigerant imbalance can cause the coils to become too cold during the conversion process, which freezes the coils up so much that they can't convert the next batch of refrigerant coming through.

Do you suspect a refrigerant problem? Call an HVAC technician. as only a professional can work with the hazardous refrigerant chemicals.

Leaking Furnace: Frozen Coils and/or Drain Clog

Do you have water pooling out around the bottom of your furnace? The problem could be frozen coils tied to a refrigerant issue, or your coils could be fine and the associated drain is clogged.

Check the coils first for any signs of freezing, then call an HVAC tech to work on the refrigerant if necessary. If the coils look fine, check your drain.

Condensation naturally occurs on the surface of the coils due to the cooling process. The condensation drips off and out of the air handler and either straight down a drain pipe or into a condensate pump that then pumps the water into a drain pipe. Check the drain pipe for any clogs, using an auger if needed to clear any blockages.

If the drain pipe seems fine and you have a condensate pump, the pump itself might need replaced.