Central Heating Not Working? Let's Troubleshoot

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When it's not used during warmer months, parts of your central heating system can become dirty or lose their functionality altogether. It's best not to wait until cold weather creeps in to power on the system and find your central heat not working.

Regular maintenance can help your furnace heat your home efficiently, but some problems are inevitable. So what should you do when you're standing at your thermostat thinking, "Why is my heat not turning on?" Before you call a repair technician, try these fixes to six common problems that you can solve at home, and you may be able to get your central heating working again.

1. Issue: Dirty Flame Sensor (Gas Furnace)

How to Spot the Issue:

Carefully look at the burner on your gas furnace while someone powers on the heater in your home. If the flame ignites but turns off after a few seconds, you may have a dirty flame sensor.

Possible Solutions:

This is one of the heater components that can become covered in dirt and debris while sitting unused, and if the sensor doesn't sense a flame, it can be responsible for central heat not kicking on. Try cleaning the flame sensor by first cutting off all power and gas, and then finding the flame sensor (a metal rod) using your HVAC owner's manual. You'll typically need to unscrew a hex screw to access the flame sensor, and, once detached, you can clean it with a coarse material like steel wool or sandpaper.

If you notice any damage to the flame sensor while cleaning, this could also be the reason for your heater malfunctioning, and it should be replaced.

Note: Don't overly scrub the flame sensor to the point that it becomes stripped or polished, as this can damage it. Simply remove any debris buildup.

2. Issue: Pilot Light Malfunctioning (Gas Furnace)

How to Spot the Issue:

Many homeowners know where the pilot light on their HVAC system is, but if you don't, check your owner's manual.

Possible Solutions:

If a malfunctioning or unlit pilot light is one of the reasons for central heating not working, you or a technician from your utility provider can easily relight it. If your home isn't getting warmer and you notice anything but a strong, blue-colored pilot light, you may need to clean your HVAC system to ensure proper, full-strength heating. Clean your pilot light's orifice to make sure the flame stays strong and clean the unit's thermocoupler to ensure it can sense the flame. If your thermocoupler is dirty, it won't be able to detect a flame and may shut off your gas valves. Check for drafts near the light, as sometimes these can blow out a pilot light.

If your pilot light won't stay on even though you don't detect drafts near your unit, it's possible your thermocouple is malfunctioning and not detecting the flame. A thermocouple is a sensor that measures temperature. Locate the thermocouple using your owner's manual, then clean the component and visually inspect it for damage. When replacing the thermocouple, make sure it fits snugly beneath the pilot so it can properly detect a flame.

3. Issue: Thermostat Not Working

How to Spot the Issue:

If your thermostat is the cause of central heating not turning on, you may notice that it doesn't look powered on, or it won't turn on the fan function.

Possible Solutions:

If you have an electric thermostat that's not working, the screen may be dark and blank, indicating a power issue. For battery-operated thermostats, the fix can be as simple as changing the batteries. For hardwired electric thermostats, you'll need to check the circuit breaker and possibly the wiring to the thermostat for damage.

Manual thermostats are prone to collecting dust inside, so if you notice yours malfunctioning, remove the cover and clean the interior with a duster, soft brush, or compressed air. If you've thoroughly inspected the thermostat and still find the central heat not working, you may need to replace the thermostat.

4. Issue: Dirty Air Filter

How to Spot the Issue:

HVAC air filters should be checked regularly to maintain good air quality in your home. If you check yours regularly, you should be able to tell if there's a problem related to your central unit not blowing heat.

Possible Solutions:

If your HVAC system and thermostat are working properly, something could be obstructing the hot air from reaching vents. When your air filter becomes too dirty, it prevents air from flowing freely through the HVAC system and your home. You should change the air filter every three months to maintain air quality and airflow. Even small maintenance tasks like this one can help you save on heating repair costs in the long run.

5. Issue: Blocked Vents & Grilles

How to Spot the Issue:

If your thermostat and HVAC system are working normally and you can hear the unit running, air filters may not be the problem. Look around your home for the central air vents and grilles. One or more may have become blocked with furniture or décor.

Possible Solutions:

Vents are typically placed to evenly distribute air throughout the home, so even one blocked vent can make it feel like a room isn't being heated. Check and clean the vent grilles thoroughly. If your vents have registers (shutters that allow you to control airflow by sliding a tab up and down), also make sure that these are open and free of debris.

You may also need to remove vents and check for any obstructions in the ducts.

6. Issue: Fan Not Functioning

How to Spot the Issue:

The best way to tell if the fan in your HVAC system's blower unit is working is by watching or listening to it while the system is active. Listening for correct operation can be difficult unless you have experience or training.

Possible Solutions:

As your HVAC system creates hot air, it relies on a fan to move it into your ductwork and through vents. If this fan has stopped functioning, you'll find your central unit is not blowing heat into your home. While there could be an issue with the fan itself, it could be an issue with the blower motor or the belt that connects the motor and fan. If damaged or malfunctioning, all three of these components should be inspected and possibly repaired or replaced by a qualified repair technician.

After inspecting the components above, if you're still scratching your head, wondering "Why is my central heat not working?" then it's time to call a professional. One way to save on heating repair is with HVAC home warranty coverage, which can help eliminate surprise costs when a covered component breaks down.

The contents of this article are provided for general guidance only. First American Home Warranty does not assume any responsibility for losses or damages as a result of using this information.

Please be aware that if you disassemble a covered system or item, it can invalidate your home warranty or manufacturer's warranty.