- 1). Check your filters before making any changes to your furnace. The National Association of Home Builders lists changing your filters regularly as one of the top ways you can save energy and maintain your furnace. A dirty filter may cause your furnace to overheat due to lack of airflow. Replace dirty furnace filters with new filters of the same size, making sure to point the printed arrows on the filters in the direction of airflow.
- 2). Listen to the furnace as it starts in order to determine what processes (such as ignition or the start of the fan motor) are occurring normally. When troubleshooting, always start with the most common problems. Make sure the thermostat is set properly. Check the circuit breakers. Feel at the registers to see if air is blowing. Listen at the furnace for the motor running. Feel the plenum for heat.
- 3). Check that the furnace has power. Newer furnace control boards have an LED light to indicate whether the power is on. These LED may give you "error codes," by blinking a certain number of times to indicate what is wrong. All error codes are different, so you find the diagnostic chart for your furnace. This will be on one of the furnace doors or in the user manual.
- 4). Observe the ignition. If there is no ignition, there is no heat. Gas furnaces have either electronic ignition or a pilot light to light the main burners. For years, gas furnaces relied on a thermocouple to maintain the pilot light. Thermocouples often need to be replaced. Shut off the gas and turn off the power. Find the thin copper tube going from the gas valve to the pilot. This is the thermocouple that sticks in the pilot to detect the flame. Unscrew the thermocouple from the gas valve and the pilot assembly. Clean the head of the thermocouple with steel wool or replace it with a new one. Turn the gas back on and relight the pilot.
- 5). Check the motor. If you have flame that shuts off within a few minutes without warm air blowing, you may have a bad motor. Try turning on the fan by itself at the thermostat. Switch the "Fan" switch from "Auto" to "On." If the fan does not start, check the fan belts, capacitors and motors.
Air Conditioning Repair
- 1). Set the thermostat to "Cool" and turn the temperature setting below the current temperature of the house. You must now determine that the air is blowing and that the air is cool.
- 2). Feel at the registers for air movement. If no air is blowing, but the outdoor condensing unit is running, you may have a bad motor in the furnace. Other reasons for a lack of airflow include a dirty or clogged air filters, broken fan belt, bad motor capacitor, or a frozen evaporator coil.
- 3). Go to the outdoor condensing unit. If you have airflow inside, but no coldness to the air, the outdoor unit may not be running. Check the fan in the outdoor unit to determine if it is running. If it is not, check the circuit breakers.
- 4). Remove the screws holding the control panel cover on the outside unit. Use a voltage meter to test for 220- volt power at the contactor in the outdoor unit. If you are unfamiliar with heating and air conditioning repair and electrical systems, this should be done by a qualified professional technician. Test the electrical contactors, capacitor, 24-volt wiring, compressor and the 220-volt wiring. Refer to the electrical schematic for data.
- 5). Use a gauge set and a refrigerant cooling chart to determine if the refrigerant charge is correct.