You cannot "reset" a furnace flame sensor, but you can reset the furnace’s control board lock-out and clean the sensor to restore your heating. If your furnace burners light for a few seconds and then shut off, the sensor is likely dirty and needs cleaning.
The furnace reset button is usually a small red or yellow button located inside the blower compartment on the side of the burner box or near the blower motor. You will likely need to remove the front panel of the furnace to access it.
A flame sensor is a safety device that detects a flame. If no flame is detected, it signals the control board to turn off the gas supply, preventing a gas buildup. A dirty or faulty flame sensor could cause your furnace to not ignite.
How to Safely Reset Your Furnace's Flame Sensor
The heat exchanger is often considered the most costly part of a furnace to repair or replace. It is a critical component that transfers heat from the combustion process to the air that circulates throughout your home. Over time, heat exchangers can crack due to the constant heating and cooling cycles they undergo.
What fails first on a furnace? The most common early failures are the furnace ignitor or flame sensor, as they experience regular wear and tear and are critical to starting the heating cycle.
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If it doesn't start at all, you can press the button one more time. But, if you press the reset button and your furnace goes on and turns off again, don't press the button again. Continuing to press the reset button can damage your system. Doing so will pump more oil into the furnace and worsen any existing issues.
To test a flame sensor, you need to check its electrical output (microamps) while the furnace is running. A working sensor creates a tiny electrical current (flame rectification) to tell the gas valve to stay open.
6 Reasons Why Your Furnace is Not Igniting
To get your furnace to kick on, first verify your thermostat is set to "Heat" and raised at least 5 degrees above room temperature. Next, check that the furnace power switch (usually resembling a standard light switch on or near the unit) is toggled "ON".
The flame sensor ensures your furnace only runs when a flame is safely burning. Trouble signs include short cycling, no heat, and yellow flames. Common causes are dirt, corrosion, and wiring issues. Technicians can clean or replace the sensor to restore safe operation.
To reset your furnace, start by turning off the circuit breaker and furnace power, wait about 30 seconds to a minute, then turn the power back on. If your furnace uses gas, you may also need to turn off the gas for a few minutes before turning it back on.
Below, we've explained the top signs your furnace needs repairs or replacement.
If pressing the reset button yields no response, this may result from a circuit breaker that has tripped or a blown fuse connected to the furnace's electrical circuit. It's essential to verify the status of the circuit breaker in your electrical panel and ensure that the furnace's circuit is active.
If your furnace shuts off after just a few seconds of running, this could point to a flame sensor issue. This happens because the flame sensor is not detecting the flame properly, so the system shuts down as a safety precaution.
Using a Scotch-Brite™ pad, rub the sensor rod to clean it of all dirt and gunk. Do not use anything harsh like sandpaper. You can use a dollar bill to clean it. Just fold the bill over the rod and, while tightly gripping it, rub it back and forth until the rod becomes somewhat shiny.
Capacitors are used in nearly every heating system, from gas furnaces to electric furnaces to heat pumps. Even though other parts can fail, like the ignitor in a gas furnace or the compressor in a heat pump, the capacitor is by far the most common part to fail on a furnace because almost every system relies on one.
Furnace Flame Sensor Replacement Costs
Professional replacement generally falls in the $75 to $250 range, which includes the part and labor. The wide range depends on your location, the technician's service call fee, and whether the visit is during regular hours or an emergency call.
The $5,000 rule is a guideline to help homeowners decide whether to repair or replace their HVAC system. You multiply the age of your unit by the cost of the needed repair. If that number exceeds $5,000, replacing your HVAC system is often more cost-effective.
All furnaces are equipped with a reset button. They are generally red or yellow and are located inside the blower compartment. The reset button is a safety feature that will shut down the furnace when a problem is detected, often a hot or overheating furnace, before it trips the circuit breaker.
The Most Expensive Parts to Repair in a Furnace
No heat is considered an emergency, even on a mild day, because the loss of heat could indicate severe HVAC problems that could threaten the safety of your home. Gas leak – A gas, propane, or fuel-oil furnace leak is a life-threatening emergency.
To qualify, you must: Be the homeowner and occupy the house. Be unable to obtain affordable credit elsewhere. Have a household income that does not exceed the very low limit by county.