The first chilly night of fall in Marietta usually means one thing: it’s time to turn on the heat. But what if you set the thermostat, hear your furnace click, and then nothing happens? No flame, no warm air. When your furnace won’t ignite, it’s frustrating, especially with temperatures dropping. The good news is that the cause is often one small part that a trained technician can fix quickly.
Most of the heating systems A-Team Services works on in Marietta and across Cobb County are gas furnaces. Below, we explain how a modern gas furnace lights, the most common reasons it won’t, a few safe checks you can try yourself, and when it’s time to call for furnace repair.
Why Your Furnace Won’t Ignite: The Most Common Causes
Older furnaces used a small pilot light that stayed lit all the time. If you have one of those, our guide to common furnace problems and DIY solutions covers pilot light trouble. Most furnaces installed in the last 20 years work differently. When your thermostat calls for heat, the furnace runs a quick start-up routine: a small fan clears the exhaust, a safety switch confirms air is moving, an igniter heats up, the gas valve opens, and a sensor confirms there’s a flame. If any one step fails, the furnace shuts itself down to keep your home safe.
1. A Worn-Out Hot Surface Igniter
The hot surface igniter is a small part that glows bright orange to light the gas. It heats up and cools down every time your furnace runs, so over the years it can crack or burn out. Fall is a common time for it to fail, because it sat unused all summer. If your furnace won’t ignite and you never see that orange glow through the small window on the furnace, a bad igniter is a likely cause.
2. A Dirty Flame Sensor
If your furnace lights for a few seconds and then shuts off, the flame sensor is often to blame. This thin metal rod confirms there’s a flame. Over time, a light coating builds up on it, and the furnace can’t “see” the flame anymore, so it turns the gas off as a safety step. A technician can clean or replace the sensor in a short visit.
3. A Pressure Switch or Inducer Motor Problem
Before the burners light, a small fan called the inducer motor pushes exhaust out of your home, and a pressure switch checks that it’s working. If the vent pipe is blocked by leaves, a bird’s nest, or debris from over the summer, or if the motor is wearing out, the furnace won’t move on to lighting. You may hear the fan hum, then the furnace stops.
4. A Clogged Condensate Drain
High-efficiency gas furnaces, the kind with white plastic vent pipes, create water while they run. That water drains through a small line and trap. If the drain clogs, a safety switch stops the furnace from starting so water doesn’t back up into the system.
5. The Gas Supply Is Off
Sometimes the gas valve near the furnace gets turned off over the summer, or there’s an issue with the gas service to your home. If your gas stove or water heater also isn’t working, the problem may be the gas supply rather than the furnace.
6. Thermostat or Power Issues
A furnace needs power to start, even though it burns gas. Dead thermostat batteries, a tripped breaker, or the furnace power switch (it looks like a regular light switch near the unit) being turned off can all stop it from starting. A furnace door that isn’t closed tightly after a filter change can also keep it from running.
Safe Checks to Try Before You Call
If your furnace won’t ignite, try these simple checks first:
- Make sure the thermostat is set to “Heat” and a few degrees above the room temperature.
- Replace the thermostat batteries if it has them.
- Check that the furnace power switch is on and the breaker hasn’t tripped.
- Replace a dirty air filter, then make sure the furnace door is closed tightly.
- Check that the gas valve handle near the furnace is turned so it runs in the same direction as the pipe.
- Turn the furnace power off for 30 seconds, then back on, to reset it.
Try the reset only once or twice. If the furnace keeps failing to light, resetting it over and over won’t fix the problem and can make it worse.
Is a Burning Smell Normal When You First Turn On the Heat?
A light, dusty burning smell the first time you run your furnace each fall is normal. That’s dust burning off the burners after months of sitting still, and it should fade within an hour. A rotten egg smell is not normal. That can mean a gas leak. Leave your home right away and call your gas company from outside. A strong electrical or burning plastic smell is also a warning sign, so turn the furnace off and call a professional. Fall is a great time to test your carbon monoxide detectors, too.
When to Call for Furnace Repair in Marietta
Call a professional if your furnace won’t ignite after the safe checks above, if it lights and shuts off again and again, if you hear clicking without a flame, or if a light on the furnace is blinking an error code. These problems involve gas, electrical parts, and safety switches, so they’re best handled by a trained technician. Our heating services team helps homeowners across Marietta, GA, and the surrounding area get their heat back on.
If your furnace is 15 years old or more and needs repairs often, it may be time to think about a furnace replacement. A newer furnace can be more reliable and more efficient. You can see our pricing, and we offer financing options to help make a new system fit your budget. If your home uses a heat pump instead of a gas furnace, learn more about our heat pump repairs and installations.
Prevent Ignition Problems with a Fall Tune-Up
Many of the problems that keep a furnace from lighting, like a dirty flame sensor, a worn igniter, or a clogged drain, can be caught during a seasonal tune-up. Our Service Club keeps your system on a regular maintenance schedule, and you can check our current specials before you book. For more ways to get ready for cooler weather, read Winter Warmth 101: Seasonal HVAC Care in Marietta.
Don’t wait for the first cold snap to find out your furnace won’t ignite. Call A-Team Services at 770-516-5165 or contact us online to schedule furnace repair or a fall tune-up today.
