A furnace that sounds like it wants to start but doesn't is usually stopped by a safety switch, a clogged air filter, or a failed igniter. The most common DIY fixes include checking the breaker, resetting the system, replacing dirty filters, or clearing a blocked pressure switch.
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".
If your thermostat clicks but the furnace doesn't turn on, it could be due to a tripped circuit breaker, a malfunctioning ignition system, or a clogged air filter. It may also indicate an issue with the furnace's control board or a gas supply problem.
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.
5 Warning Signs It's Time for Furnace Replacement
Most furnaces last between 15 and 20 years. However, exact longevity depends heavily on your system type, usage, and maintenance habits.
To diagnose a furnace issue, start by checking the thermostat settings and ensuring it's set to "heat" and at the right temperature. Inspect the air filter for clogs and replace if dirty. Ensure the furnace switch and circuit breaker are on.
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.
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.
As the filter becomes more clogged, it can cause other parts of the furnace, such as the blower motor or heat exchanger, to overwork and eventually fail. Replacing these components can be costly, and in severe cases, you might even need to replace the entire furnace.
To determine if your furnace fuse is blown, turn off the power to the unit, remove the automotive-style fuse from the control board, and inspect it for a broken metal filament or dark burn marks. Alternatively, use a multimeter to check for electrical continuity.
When your furnace clicks but refuses to turn on, it typically means the electronic ignition sequence has failed. This is often caused by a dirty flame sensor, a cracked or burnt-out igniter, or a faulty gas valve.
A frozen pipes furnace failure can cause major problems inside your home. Ice builds up fast in unheated spaces, and when frozen water expands, it can burst pipes wide open. That kind of mess is the last thing anyone wants during a winter heating outage.
When your furnace suddenly stops working, it is usually caused by a tripped breaker, a dead thermostat battery, or a clogged air filter. Before calling a technician, you can quickly check a few key areas to potentially restore your heat safely.
You can only safely and manually light a furnace if it has a standing pilot light system. If you have a newer furnace with an electronic ignition (hot surface igniter or spark igniter), never attempt to manually light it, as this poses a severe risk of explosion and fire.
You may feel this is the easiest and most harmless step, but the reset method is not the same for all types of systems, and it is not right to reset your system frequently. If you face the same problem more than once or twice, do not reset your system every time. It will damage your furnace.
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.
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.
Heating Schedules. Keep to a steady heating schedule over winter to keep a home consistently cozy. HVAC technician Josh shares, 'On average, in winter weather, most furnaces or boilers will cycle on and off for eight to 12 hours per day. That's assuming daytime temps around 35-45°F (1 to 7°C) and nights in the 20s.
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.