If your furnace turns on (the blower fan or inducer motor runs) but no flame ignites, the issue is typically a gas supply problem, a dirty flame sensor, or a failed ignition component. Follow these steps to safely troubleshoot the issue:
If your furnace has power (like a glowing thermostat or active diagnostic light on the control board) but won't start, the issue usually stems from a safety mechanism blocking ignition, restricted airflow, a tripped limit switch, or a loose blower door panel.
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 furnace is not turning on, start with the basics: ensure your thermostat is set to "Heat" a few degrees above room temperature, check that the breaker in your home's main electrical panel hasn't tripped, and verify the physical power switch located on or near the furnace is turned on.
To safely reset your furnace, turn off the power at the service switch (usually located on or near the unit) or the breaker panel. Wait 3 to 5 minutes, then restore power. If it has a physical safety trip, locate the limit switch or rollout button and press until you hear a click.
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.
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.
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.
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 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.
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.
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.
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".
Signs of a failing control board include the furnace not starting, the blower fan running nonstop, flashing error codes on the unit, and the system not responding to the thermostat.
The most obvious signs of frozen pipes are a sudden drop in water pressure (or no water at all when you turn on a tap), visible frost or condensation on exposed piping, and strange clanking or gurgling sounds when water runs.
To prevent your water pipes from freezing during an extended outage, you should drain the water from your plumbing system. Here's how: Shut off the main valve that brings water into your home. Starting at the top of your house, open all faucets and flush all toilets several times.
As temps drop, the risk of having frozen pipes in your home increases. Typical high-risk areas for freezing include pipes within exterior walls, as well as exposed pipes that run through unheated or uninsulated areas such as attics or basements.
5 Warning Signs It's Time for Furnace Replacement
Your furnace’s reset button is typically a small, bright red or yellow button located either inside the blower compartment, near the burner assembly, or directly on the motor housing.
If the temperature in the furnace rises above a safe level, the limit switch will then trigger the reset button, shutting down the furnace to prevent further damage or unsafe conditions. This mechanism helps avoid more serious issues, including tripping your circuit breaker.
Short cycling
This is one of the most common furnace problems, and it can stress important furnace components such as the blower motor, limit switch, or flame sensor. There are several potential causes of short cycling, including some that are related to your furnace's built-in safety systems.
If your furnace is not turning on, start with the basics: ensure your thermostat is set to "Heat" a few degrees above room temperature, check that the breaker in your home's main electrical panel hasn't tripped, and verify the physical power switch located on or near the furnace is turned on.
Gas furnaces and oil furnaces often require more detailed checks than electric furnaces, which can affect the overall inspection cost. A furnace inspection typically costs between $50 and $300, with an average cost of $100. Scheduling a furnace inspection in the off-season, such as late summer, can save you money.