How do I Troubleshoot an Induction Furnace?

Check that the furnace has power. When the furnace was installed, a power switch that looks exactly like a light switch should have been installed as well. To avoid confusion, they are normally installed on the ceiling or directly beside the furnace, but not always. One of the home's occupants may have gone into the furnace room and tried to turn on the lights. When the first switch did not work, they may not have thought to flip it back before trying another switch.

Check for the presence of a flame. If the inducer motor comes on, the hot surface igniter turns bright orange and the flames start but then stop shortly after, the flame sensor is not functioning. The purpose of the flame sensor is to verify the presence of the flame to prevent gas from continuing and building up.

Monitor the blower to ensure that it comes on. If the furnace starts up but the blower does not turn on shortly after, the heat exchanger will begin to overheat. This excessive heat will trip the high limit switch and shut down the furnace. This can also take place if the fan setting is too low, which also allows excessive heat to build up.

Check that the inducer motor is running. The inducer motor is the first thing that you see working and if it shuts off shortly after starting, there may be a block in the venting or a defective pressure switch. Check the venting outside and make sure there is nothing blocking the airflow, such as snow, dirt or anything in front of the vent. Check that nothing has crawled into the vent, as this will cause an immediate blockage. Leave the testing of the pressure switch to the technician to protect your warranty and the furnace from damage due to incorrect handling.

Check that the filter is clean. A dirty filter will block necessary airflow and can overheat the heat exchanger causing the furnace to turn off. A dirty filter will also force the furnace to work harder, which shortens the life of the furnace.

Test the thermostat to verify it is functioning properly. If the wires were not connected securely when the thermostat was installed, they may have come lose and are no longer making contact. Open the faceplate and check the wires by giving a gentle pull to see if any move.