Winter weather is starting to set in here in Cincinnati, OH. If you know Ohio weather then you know that could mean a random 60-degree spring day at times, but most likely it will mean a lot of bitterly cold days and not a lot of sunshine. During these times it is crucial that your furnace starts up and heats properly so you can stay comfortable.
If your furnace won’t turn on there are a few simple DIY things you can check before calling for a furnace repair pro. We’ll go through how to check some reasons why your furnace won’t start up.
Go to your breaker box and check to see if a breaker has flipped (hopefully your box is nicely labeled so the furnace breaker is easy to find!) This is still important to check even if you have a propane or gas furnace. If you find the breaker is in the “off” position, try turning it back on to see if that fixes the issue. If the breaker repeatedly trips, then it is time to call for HVAC repair. If other appliances are also not working, the chances of it being an electrical problem are probably high.
It sounds simple, but make sure that your thermostat is in heat mode and turned on. We’ve gotten a lot of calls from thermostats simply still being set to AC mode.
If the thermostat display is not lit, then you may need to change the batteries.
Finally, check to make sure you don’t have a schedule set that may be keeping it cooler in the house than you would like. When using a programmable thermostat with scheduling features you may have it set to be cooler during times of day when you’re typically not home.
A dirty filter could reduce the air flow in your furnace. We often find that clogged filters are the culprit for why a furnace won’t kick on. If you do find that your filter is rather dirty, go ahead and change it and wait a couple hours before reassessing if you do need a service call.
How to find your filter:
The furnace filter is normally located inside the blower compartment. Where the blower is just depends on how your furnace was installed.
Common areas the filter will be:
If you have a gas furnace, you can check to make sure your pilot light is still lit. You will find the pilot light by looking in a little see-through panel on the front of the furnace door. If it’s lit, you will be able to see a flame. If it isn’t, this means there is no gas supply to your furnace. This could be due to a number of reasons, including a safety issue that has caused your furnace to shut down out of caution. If you find your pilot light has gone out, call for professional furnace service.
READ MORE: How to Light a Furnace
If your furnace is very new or highly efficient there may not be an easy way to check the pilot light yourself and a professional will need to check things out.
If your exhaust vent outside is blocked, it can prevent the furnace from operating. We’ve seen this happen many times after a heavy snow when the snow was deep enough to cover the exhaust pipe. Simply clear the obstructions from the pipe and the furnace should resume working normally if that was the culprit.
If the access panel on your furnace is ajar or improperly closed, it can prevent the furnace from starting. Most modern furnaces are equipped with safety switches that ensure the access panel is securely in place before allowing the system to run. This is a precaution designed to protect homeowners and technicians from potential hazards, like exposure to electrical components or moving parts. If the panel is not fully closed, the switch won’t engage, and the furnace will remain off or fail to start. Always make sure the access panel is properly aligned and securely fastened after any maintenance or inspection to avoid this issue and keep your furnace running safely.
One last area you can check when your furnace won’t start is the furnace switch. This can be on the side of the unit or mounted on the wall. This switch is responsible for the power to the furnace. If it is off, turn it back on and see if this restores proper heating operation. If it will not stay on, then it’s time to call for professional repair.
If you’ve gone through the entire troubleshooting list above and your furnace still won’t start with any of those simple fixes then it’s likely you have a deeper issue going on. At this point it’s best to call for professional furnace repair, but here we’ll give you a list of likely culprits that are causing your furnace not to turn on.
A dirty flame sensor can prevent a furnace from starting because the flame sensor is a critical safety component designed to detect whether the burner is producing a flame. When the furnace ignites, the flame sensor confirms that the gas is being burned properly. If the sensor is dirty or coated with grime, it may not detect the flame correctly, causing the furnace to shut down as a safety precaution to prevent unburned gas from accumulating. This can result in the furnace attempting to start but shutting off shortly after or failing to start at all. Cleaning the flame sensor is a relatively simple task and is often the solution to this issue, restoring normal furnace operation. Regular maintenance can prevent this problem and keep the furnace running smoothly.
A bad blower motor can prevent a furnace from starting because the blower motor is responsible for circulating warm air throughout your home. When the furnace ignites and heats up, the blower motor kicks in to distribute the heated air through the ductwork. If the motor is faulty or completely fails, the furnace’s internal controls may prevent the system from starting as a safety measure to avoid overheating. Without the blower functioning, heat would build up inside the furnace, potentially damaging components like the heat exchanger. As a result, the furnace will either shut down entirely or fail to complete its heating cycle. Signs of a bad blower motor include unusual noises, weak airflow, or the furnace shutting off prematurely. Repairing or replacing the motor is necessary to restore normal furnace operation.
In order to check your furnace blower motor, peek through the plastic window on the front of the furnace. It is possible that, depending on the brand, your furnace does not have this window. If it does, know that different furnace brands may also have different light indicators for regular operation or error codes. Typically, a red/yellow/green light that is continuously illuminated or is flashing in a regular pattern indicates normal operation. A red, yellow or green light that is flashing quickly, then slowly or at other variable patterns most likely indicates an error code. Further inspection into the blower motor should be done by a professional HVAC company.
We’ve gone over how to check your furnace components when the furnace won’t start. If none of these seem to solve your furnace start-up problem, then give an HVAC professional a call. If you’re in the Cincinnati, OH area, Quality Comfort Home Services would be happy to help!
