Your furnace is supposed to fire up, run for 10 to 15 minutes, and shut off. Instead, you hear the inducer motor spin, the igniter glow, and then… nothing. No flame. The whole sequence repeats a few times and the system locks out.
This is one of the most common no-heat calls we run in Rock Hill. The good news: about a third of these are fixed by a homeowner in 10 minutes without spending a dollar. The other two-thirds need a licensed technician. Here is how to tell which one you have.
The Five Most Common Ignition Causes
When a furnace fails to ignite, the cause is almost always one of these:
- Dirty flame sensor. The most common cause we see. The flame sensor is a thin metal rod near the burners. When it gets coated in oxidation, the control board cannot confirm the flame, so it shuts the gas off as a safety measure. Easy fix for a technician, but should not be DIYed because it sits right next to gas burners.
- Failed hot surface igniter. Igniters are a wear part. They glow red-hot to light the gas, and after 4 to 7 years they crack or burn out. If your furnace clicks on, you hear gas flow, but nothing lights, this is the most likely culprit.
- Clogged air filter. A dirty filter can trip the high-limit safety switch, which prevents ignition until the system thinks the airflow is safe.
- Thermostat or wiring issue. A dead thermostat battery, miscalibrated thermostat, or loose wire can stop the call for heat from reaching the furnace at all.
- Gas supply problem. Closed gas valve, tripped meter regulator, or an empty propane tank. Less common but easy to miss.
Safe DIY Troubleshooting (Do These First)
Run through this checklist before you call anyone. These are all safe homeowner checks.
1. Thermostat
- Confirm the mode is set to Heat, not Cool or Off.
- Confirm the setpoint is at least 3 degrees above current room temperature.
- If your thermostat takes batteries, replace them. Low batteries cause weird intermittent behavior.
- Some smart thermostats need a C wire. If yours was working and now is not, check the app for power-related warnings.
2. Circuit Breaker
Walk to your electrical panel. Find the breaker labeled Furnace or Air Handler. If it is in the middle (tripped) position, flip it fully off and then fully on. If it trips again immediately, stop. That is a short circuit, and you need a licensed technician.
3. Power Switch
Most furnaces have a switch that looks like a regular light switch mounted on the side of the unit or on a nearby wall. Confirm it is on. We have driven out for no-heat calls where a kid bumped the switch with a vacuum.
4. Air Filter
Pull the filter. If you cannot see light through it, replace it. Then wait 15 minutes for any high-limit safety to reset, and try the system again.
5. Gas Valve
Look at the gas line going into the furnace. There is a quarter-turn shut-off valve. The handle should be parallel to the pipe (open). If it is perpendicular, turn it parallel.
For propane: check the tank gauge. If it is below 20 percent, that is your problem.
When to Stop and Call
Past those five checks, you have hit the limit of safe DIY. Anything beyond this point involves either gas, high-voltage wiring, or combustion safety. Stop and call a licensed pro if:
- You smell gas, even faintly. Leave the house first, call from outside.
- The breaker trips repeatedly when you reset it.
- You hear the igniter glow but see no flame for several startup attempts.
- The furnace ignites, runs 30 to 60 seconds, then shuts off (classic dirty flame sensor).
- You see any soot, scorching, or yellow flame instead of blue at the burners.
- Carbon monoxide alarms are sounding.
Yellow flames, soot, and CO alarms are not annoyances. They are combustion problems that can be lethal. Shut the furnace off at the thermostat and at the power switch, ventilate the space, and call us.
What Atlas Does on an Ignition Call
Our $89 diagnostic gets a licensed technician on site, typically same-day in Rock Hill, Fort Mill, Tega Cay, and Lake Wylie. We run the sequence in front of you, check igniter resistance, clean or replace the flame sensor, verify gas pressure with a manometer, and confirm the heat exchanger is safe. You get a written, flat-rate quote before any parts come off the truck. Approve the repair and the $89 rolls into the bill.
That is the Atlas Standard. No upselling a $250 igniter into a $9,000 replacement. If your furnace can be honestly repaired, we repair it.
Preventing the Next Ignition Failure
Most flame sensor and igniter failures we see are on systems that have not had a fall tune-up in 2+ years. A proper tune-up cleans the flame sensor, checks the igniter for hairline cracks, and verifies the burner is firing cleanly. Our Atlas Assurance membership bundles fall furnace and spring AC tune-ups, plus priority scheduling and a 15 percent repair discount.
For related troubleshooting, see our guide on signs your furnace needs immediate repair.
Get Heat Back On
If you have run through the homeowner checks and the furnace still will not light, call (803) 839-0020 or schedule online. Same-day service across York County. Written, flat-rate pricing before any repair starts.
