Signs a Furnace’s Thermostat is Damaged

Check that the thermostat switches aren't loose or broken.

Problems with a furnace sometimes arise, either suddenly or gradually. It may take longer to warm up the living space, or the home frequently feels overheated. The furnace may run long after the home is heated, making inhabitants uncomfortable and increasing home heating costs. Whatever the circumstance, the likely cause is a faulty thermostat.

Thermostats hold a lot of power over the comfort of a home. Adjusting the temperature of the furnace thermostat too frequently can cause damage. If the furnace is under or overheating the home, it's likely an issue that can be repaired. However, these issues sometimes call for total replacement of the thermostat. Consider the following causes of why a thermostat isn't working properly and must be either repaired or replaced.

Thermostat switches

Check that the thermostat switches aren't loose or broken. Many older thermostats, especially mercury and analog models, have plastic parts that can snap off or break. If there's any play or give in the temperature adjustment switch, a new thermostat is necessary to guarantee the efficiency and reliability of the furnace.

Dirt, dust, or debris

Remove the cover to the furnace thermostat and eyeball the interior. If there's a build-up of dust, grease, or debris inside, use a can of compressed air to spray away the dust gently. A small, soft paintbrush may also be able to clean the tight spots.

Loose wires

Look closely for any loose wires or broken components in the thermostat unit. This issue is likely too complicated for most homeowners to fix on their own, so contact a professional to assess if it is fixable or if the thermostat needs replacing.

Internal battery

Using an electric controller, check to see if the internal battery within the furnace thermostat is discharged. If so, reference the thermostat's manual for guidance and replace the battery.

Once the thermostat has been inspected with no apparent problems, turn the furnace back on and wait to see if it's working correctly. If the furnace doesn't engage, shuts off suddenly, or runs without normal interruption, call a professional to better assess the situation, as it's likely beyond the capabilities of the average homeowner.

Many homeowners try to replace or repair their furnace thermostats independently, but it's a complex fix for those unfamiliar. For those who feel uncertain about dealing with the electrical components of a home heating and cooling system, or if the cause of the issue needs to be clarified, call the professional HVAC specialists. These experts have the knowledge and experience to quickly identify and repair an HVAC system and return it to working condition.