If your furnace is running and the blower won't shut down, your power bill may run up, and even worse, your furnace might overheat and be damaged. A furnace that won't shut down isn't always a serious problem, but since it can be, you want to find the cause and fix the problem right away. Here are some reasons a furnace doesn't shut down and how a heating services contractor might help.
1. Airflow Might Be Blocked
Check the filter in your furnace to see if it's all dusty. If so, change the filter to see if the blower will turn off. Restricted airflow affects how well the blower works, so if the problem isn't the filter, you may want to check the registers to make sure none are covered and blocked.
2. Airflow Might Be Leaking
A busted duct might be the issue because heat may be leaking out in the attic and not making it to your living space. This causes the furnace to keep running because the temperature in your house never reaches the setting on the thermostat. If you can't seal the duct leak yourself, call a heating services company to check and seal the duct or replace it.
3. The Thermostat Is Bad
Check the thermostat settings just to make sure no one moved them and has the heat setting too high. If the settings are correct, there could be an internal issue with the thermostat or with the wiring from the thermostat to the furnace. You may need a heating contractor to track down the location of the problem and fix the wiring or replace the thermostat.
4. The Limit Switch Is Bad
The limit switch is a part that controls the blower. If the switch is bad, the blower may not get the signal to shut off. The switch is also a safety device that shuts the furnace off if the furnace overheats, so it's important that the switch is operational. A heating services contractor can check the switch to see if it's bad, and if it is, they can replace the switch with a new one and then wait to verify the furnace will shut off.
If the furnace gets too hot and the switch isn't able to turn off the furnace, parts of the furnace might crack or parts might overheat and go bad. That's why a furnace that won't shut off should be checked by a professional. This ensures your furnace operates safely and properly to protect you and the equipment.