What to Do When Your Thermostat is On But Furnace Isn’t Running

When winter arrives in Amarillo, a reliable furnace keeps your home comfortable and safe. If your thermostat says the heat is on, but your furnace isn’t running or heating your home as it should, confusion and frustration are normal responses.

Several problems can prevent your furnace and thermostat from communicating properly. When you understand the underlying causes of heating system malfunction, whether a faulty thermostat or a more complex furnace problem, you can address them more quickly and effectively. Learn the common causes of thermostat and furnace problems, troubleshooting tips, and when to call an HVAC professional for assistance.

Common Reasons Your Thermostat Says the Heat Is On But Furnace Isn’t Running

The thermostat and furnace work together to regulate heating cycles and your indoor temperature by detecting and communicating temperature shifts to your furnace. If the thermostat malfunctions, it can disrupt your heating system’s efficiency and function, sometimes resulting in no heating at all.

The thermostat continuously monitors your home’s temperature using a built-in sensor. When the temperature drops below the set point, the thermostat sends a signal to the furnace’s control board to trigger a heating cycle. As the furnace heats and circulates air, the thermostat continues monitoring the temperature. When it reaches the set point, the thermostat sends another signal to end the heating cycle. This cycle repeats throughout the day to respond to temperature fluctuations and maintain consistent heating.

Faulty components in your furnace or thermostat can cause your thermostat to click, but no heat comes on. Here are several common reasons why your heat isn’t turning on.

Unresponsive thermostat

Thermostats can accumulate dust in and around the unit, affecting its function. If dust builds up on the temperature sensor, it may be unable to accurately detect temperature. These sensors wear over time and eventually lose function. In either case, your thermostat can’t communicate temperature fluctuations or trigger a heating cycle if the sensor is faulty or unresponsive.

Incorrect programming

If your furnace doesn’t turn on, the thermostat may need reprogramming. A household member may accidentally or mistakenly adjust the set point, setting it too high to consistently trigger the furnace. Dead batteries, power surges, or wiring problems can also reset the programming.

Faulty wiring

Improper wire configuration during installation prevents your thermostat from signaling your furnace. Copper wiring is durable, but wear may damage insulation or cause corroded, fraying, or loose wiring, preventing it from operating properly.

Miscalibration

If your thermostat appears to be in good condition and correctly installed and programmed, it might have calibration issues. Calibration ensures the thermostat accurately reflects the temperature — miscalibrated thermostats may read the space as cooler or warmer than the actual temperature. For example, if the set point is 65 degrees but the thermostat reads a 63-degree room as 67, it won’t activate the furnace.

Disconnected power supply

A tripped breaker or blown fuse connected to the furnace or thermostat prevents them from operating. The furnace itself may be disconnected or switched off, or the thermostat may have dead batteries.

Airflow problems

In some cases, the furnace may be on and heating air but unable to circulate it.  Airflow issues stem from several potential issues, including:

• Faulty blower
• Blocked vents or ductwork
• Clogged air filter

Ignition system malfunction

A damaged ignitor or pilot light problems may prevent your furnace from turning on. Faulty gas valves or line blockages can also disrupt fuel supply, likewise preventing ignition. These problems are usually characterized by repeated clicking or popping, indicating failed or delayed ignition.

Faulty safety sensors

Furnaces feature safety sensors that shut down the unit when triggered by unsafe conditions, such as internal furnace temperature or an absent burner flame. If these sensors become dirty or malfunction, they may falsely detect shutdown conditions and prevent the furnace from starting.

Faulty control board

The control board directs signals between various components to safely and efficiently coordinate furnace mechanisms, such as ignition. If the control board malfunctions, it may fail to respond to thermostat signals and cause erratic heating.

Troubleshooting a Non-Responsive Furnace

Identify or rule out basic issues with these troubleshooting tips:

1. Check the thermostat, ensuring it’s set to heat.
2. Verify the thermostat programming. The set point should be between 68 and 70 degrees.
3. Reset the thermostat if necessary, either with the reset button or manually — turn it off, and either flip off the circuit breaker or remove the batteries. After 30 seconds, restore power and turn the thermostat back on. Set the temperature.
4. Ensure the power switch and circuit breaker for the furnace are on.
5. Inspect the air filter, replacing if necessary.
6. Locate the gas cutoff valve, and check that the gas supply is on. If you suspect a gas leak, exit your home and call a professional.

When to Call a Professional for Furnace Repairs

If troubleshooting hasn’t resolved your heating concerns, your furnace might have more complex problems that require professional HVAC repairs.

While some heating system repairs are straightforward, such as switching on a tripped circuit breaker, others require specialized tools and expertise that present significant challenges to homeowners. DIY repairs might seem cost-effective, but they often fail to correctly identify and resolve the underlying problem, sometimes leading to further damage and higher repair costs.

In comparison, licensed HVAC technicians provide a precise diagnosis and fix. Investing in professional furnace repairs minimizes the chance of recurring problems, saving you on repair costs in the long term.

Preventative Tips to Keep Your Furnace Running Smoothly

Try these preventative maintenance tips to avoid inconvenient breakdowns and keep your furnace running smoothly and efficiently:

• Regular maintenance: Schedule annual inspections and maintenance with an HVAC technician to catch furnace issues before they escalate and cause premature wear.

• Air filter changes: Depending on usage, replace air filters at least every three months.

• Thermostat tests: Routinely check your thermostat’s settings to ensure accurate set points and temperature readings.

• Thermostat upgrades: If you use a manual thermostat, consider upgrading to a programmable or smart thermostat. These devices help optimize system efficiency, prevent undue wear, and sometimes provide diagnostic codes.

• Vents and ductwork: Clean ductwork periodically and keep vents open and unobstructed by furniture or other items. Seal minor duct leaks or schedule ductwork repair as needed.

• Insulation: Proper insulation prevents heat loss and reduces the workload on your furnace.

Don’t Wait in the Cold — Schedule Your Furnace Repair Appointment in Amarillo, TX Now!

If your thermostat clicks but nothing happens with your furnace, take prompt action to restore efficient heating and comfort to your home. Serving Amarillo, Canyon, and Bushland in Texas, Amarillo Air is the preferred choice for heating system repairs, maintenance, and more. Our expert furnace technicians are ready to ensure your home stays warm all winter — contact us or schedule a service online.