The most common sign of a bad or dirty flame sensor is short cycling: the furnace burners ignite, but the flame shuts off almost immediately (usually within 3 to 10 seconds). This happens because the sensor fails to detect the flame and shuts off the gas valve as a safety precaution.
Attach one wire from your multimeter to the flame sensor wire and the other one to the unit where you unplugged the wire. Turn on the unit. Look for a reading between. 5 and 10 micro-amps with the normal range between 2 and 6.
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.
How to Safely Reset Your Furnace's Flame Sensor
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.
Like most parts of your heating system, the flame sensor can wear out or get dirty over time. Common reasons it stops working include: Buildup of dirt or soot: A thin layer of debris can block the sensor's ability to detect a flame. Corrosion: Moisture and combustion gases can corrode the sensor's metal rod.
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.
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.
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.
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.
A furnace flame sensor should generally be cleaned once a year, usually at the start of the heating season. However, homes with pets, heavy dust, or appliances that produce airborne debris (like laundry lint) may require cleaning more than once a season.
Visual Inspection
Start by turning off your furnace power to stay safe. Look carefully at the flame sensor's metal rod. Check if it's dirty, rusty, or coated with soot. Dirt or buildup can stop it from sensing the flame properly.
Furnaces should cycle 3-8 times per hour. Short cycles may indicate oversized units or airflow issues. Long cycles can signal undersized furnaces or insulation problems. Regular maintenance helps ensure proper cycling and performance.
Dust, other contaminants, vibrations, shocks and exposure to high temperatures all have a shortening effect on the average lifespan of a sensor, so it is important to look for a solution that overcomes these problems by design, rather than just accepting frequent sensor failure and replacement as part and parcel of ...
Is yearly furnace maintenance necessary? It's recommended, as annual furnace maintenance can spot potentially dangerous issues early on. For example, a gas furnace inspection could reveal a cracked heat exchanger.
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".
To fix a furnace that is short cycling (turning on and off rapidly without completing a full heating cycle), first replace your clogged air filter, check that all room registers are open, and ensure the outdoor exhaust vent is clear of debris.
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.
Try the Salvation Army, a local church, or a community action agency. Their rules may be different. Ask About Payment Plans: Many local HVAC contractors, including Smart Climate Solutions, offer payment plans for urgent repairs because we believe everyone deserves a warm home.
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.
Furnaces, like people, can suffocate when you restrict air from going in or out of them. You can accidentally suffocate your furnace by: Closing air vents. Not changing the filter.
Most furnaces last between 15 and 20 years. However, exact longevity depends heavily on your system type, usage, and maintenance habits.
Both single-stage and two-stage furnaces typically last 15-20 years with proper maintenance. Some homeowners report that two-stage furnaces may last slightly longer because they run at lower capacity most of the time, creating less wear and tear on components.