If your furnace stays on, even with the thermostat set at a reasonable temperature, it's time to check your thermostat for problems. Although thermostats seem small and insignificant, they play essential roles in running your heating system. If your thermostat's wiring comes loose or rust, it won't work correctly. Your furnace won't know when to turn off or on. Here's how you solve your thermostat's problems.
Check the Thermostat
You'll need to remove the cover from your thermostat to access the wires inside it. First, turn off the thermostat, then gently lift the cover. If the cover comes completely off, place the cover on a soft surface to avoid damaging it. Next, inspect the wiring connected to the mounting screws on the baseplate. If the wires appear disconnected from the baseplate, reconnect them. You also want to clean, straighten, or tighten the baseplate to the wall during this step. The plate can become loose from the wall over time.
If the wires and sensors appear rusted or corroded, you can try to clean them. Use a soft ear or cotton swab to gently clean around the wires, sensors, and their connection points. To avoid electrical shocks, don't dampen the swabs with water, alcohol, or another liquid.
You can now reconnect your thermostat's cover to the baseplate. Return power to the thermostat and set it to a desirable temperate. Wait for the furnace to come on. If the appliance comes on and reaches the right temperature before cycling off, you solved the problem. If the furnace stays on without shutting off, contact an HVAC contractor for additional help.
Contact a HVAC Specialist
If your thermostat is clean and secure, you may have a problem with your furnace instead. Furnaces can stay on if there's an issue with the air filter or limit switch. If the air filter is too dirty, it can prevent air from reaching the blower motor inside the appliance. Although changing the air filter is a simple fix, there may still be a problem with the blower motor. A contractor can examine, clean, and repair the motor for you.
The limit switch tells the blower motor when to cycle on and off by sensing the temperature inside of the furnace. If the switch is broken or stuck, it won't sense the right temperature. The furnace will stay on continuously. I the furnace needs a new limit switch, a contractor can go ahead and install it.
If your furnace continues to have problems before or after the repairs, contact a heating contractor, such as at H.R. Stewart Inc., for an appointment.