Why Does My Furnace Keep Turning Off? Troubleshooting Common Issues
There are several reasons why a furnace might keep turning off. It could be as simple as a dirty air filter or something more serious like a defective heat exchanger.
Check that the thermostat is turned on and set to “heat.” Also, make sure none of your vents are closed or blocked – especially those in unused rooms.
1. Thermostat Issues
While it’s normal for a furnace to cycle on and off 3-8 times per hour, when the system keeps shutting itself off, that’s a sign of a problem. A few troubleshooting tips can help you figure out what’s going wrong with your system.
The first thing to check is the thermostat. Ensure it’s on and switched to “heat.” It may also be off or set at the wrong temperature, so double-check those settings.
Thermostat issues often involve the temperature sensor. If it’s placed in direct sunlight or near another heat source, it may get a faulty reading and assume the house is warmer than it actually is, which causes the system to turn off sooner than it should. If you suspect this is the case, have a professional come take a look. They can make sure the temperature sensor is in the right place and that it’s not getting messed up by other heating components like a supply vent.
2. Blower Motor Issues
If the furnace keeps turning off, it might be a sign that the blower motor isn’t getting enough airflow. The solution is to open your vents and clear out any clogs.
Another issue that can cause your furnace to keep turning off is a dirty flame sensor. This is a safety feature that stops the gas valve from opening if it can’t find a flame, which prevents carbon monoxide poisoning. To fix it, you’ll need a screwdriver to remove the switch on the top of your unit and clean the flame sensor. If you’re not comfortable doing this, call a local Billings HVAC professional for help.
Excessive noise from your furnace can indicate an easy-to-fix problem that could save you money in the long run. If you’ve checked your thermostat, the vents, and the filter and your system still cycles on and off, it’s time to call a pro. If you wait too long, you may end up with an expensive repair or even a replacement.
3. Dirty Filter
When your furnace keeps turning off, the first thing you should check is your filter. A dirty or clogged filter can prevent air from flowing over the heat exchanger, which leads to your furnace short cycling. You should replace or clean your furnace filter every 90 days to keep it working properly.
A corroded or soot-covered flame sensor rod inside your furnace is also a common cause of furnace short cycling. This sensor shuts off the gas valve if it doesn’t sense fire, to prevent a buildup of unburned gas and carbon monoxide.
Blocked grates and exhausts can also limit the amount of air that your blower can move over your heat exchanger, causing your furnace to short cycle. Make sure you leave at least some vents open – especially those in unused rooms. You can test airflow by holding your hand over the vents to see if you can feel the flow. If you can’t, contact a home inspection company to clear out the obstruction.
4. Blocked Vents
If your heating system keeps turning on and off, you could have a problem with the temperature sensor or your thermostat. You can try a couple of things to fix this issue. First, ensure that the thermostat is switched on and set to heat. Also, have a friend stand near the furnace and switch the setting from low to high. They should hear a sound that indicates the thermostat is communicating with the heater (if they don’t, your problems are likely elsewhere).
You should also check all of your home’s air supply vents for any closures or blockages. Closed or blocked vents slow down the blower from pulling cold air over the heat exchanger, causing it to shut off before your house gets warm enough. Make sure to open all of your vents, including those in unused rooms. Finally, you should check that the flame sensor is not covered in soot. You can remove the flame sensor with a screwdriver and scrub it with a microfiber cloth to see if the soot can be removed. If you cannot remove the soot, call a professional to clean it for you.