Your Furnace / Air Handler Filter is Dirty

dirty and clean filter


You may be surprised to know that 8 out of 10 house calls to repair an AC wind up being this very simple issue. You've got to ensure that your filter to your furnace or air handler is relatively dust free and is allowing the full force of air to pass through it.

The filter is located on the "downstream" side of your furnace or duct work. This is the return air back to the furnace or air handler fan. The filter may be located right on the outside, or inside, of the furnace/air handler cabinet that houses the motor and fan that moves air through your house. Filters may also be located at various points throughout your house if you have intakes in other areas of your home. If the latter is the case they should be easy to spot as they'll be exposed on a wall or ceiling and are typically no smaller than 14" x 14". You can get new air filters at just about any hardware store.

What happens if your filters are clogged is that warm air, or enough warm air anyways, is not making it to your indoor evaporator coil to having the heat removed from it. This means that the chilled Refrigerant just sits in the evaporator coil and begins to freeze the coil. This is because the unit will run until the thermostat kicks it off. As the evaporator coil freezes it can run all the way outside freezing the line to the condenser. So you've got to ensure the warm air is passing freely to the evaporator coil.

This also means that after replacing a clogged filter you may have to run the system for several hours to de-ice it before noticing any cool air to start flowing again.

Replace your filters regularly!


Got clean filters? Let's make sure your condenser is dissipating heat properly next: Next >>>