My Furnace Does Not Get Up to Temperature

Burner Nozzle

• There is a nozzle at the top of the burner. Sometimes the tiny opening gets clogged with dirt from the oil tank, with the result that there is only a small or no flame to heat the air. The bottom of your oil tank collects sediment from the heating oil. This sediment gets drawn into the burner nozzle when you run the tank down near empty. You are less likely to have a clogged burner nozzle when you arrange for the oil company to top off the tank monthly.

Air Filter

• If your furnace is working properly but the house is still chilly, then check for a dirty air filter. Your air filter should be changed during the yearly maintenance check. However, some filters get clogged more frequently, impeding warm airflow, when they are close to the clothes dryer. In this case, either move the clothes dryer to a different part of the basement or change the filter more frequently.

Supply Air Fan

• The supply air fan blows hot air from the plenum through the heating ducts and room registers. There could be two problems with it. The fan belt may have worn out and snapped. Replacing the belt will allow your furnace to get up to temperature. Sometimes the fan motor burns out, so minimal hot air would reach the room registers.

Ductwork

• Look for leaks in the supply line ductwork, between the furnace and room registers. Check for small holes or tears in the lining, as well as hot air escaping from the seams where the different sections connect. If the ducts do not have any leaks and the furnace is in adequate working order, then you may need to insulate the ductwork. Heat diffusion works by equalizing room temperature by pulling heat from the ductwork into the surrounding cold air of an unheated basement. Insulate the ductwork to minimize the amount of heat loss. Not only will you have a warmer home, but the furnace will not need as much oil or natural gas to reach the desired temperature, saving you money on your energy bill.

Thermostat / Flame Sensor

• A faulty thermostat will shut off the furnace before it reaches the correct temperature. A faulty thermostat cannot be repaired and you will need to replace it. If the burners turn on, but does not stay lit until the thermostat indicates the correct temperature has been reached, then your problem may be a dirty flame sensor from sediment in the oil.