When you turn on your furnace and nothing happens — no flame, no heat, just the sound of the blower pushing cold air — you're dealing with an ignition failure. This is one of the most common heating repair calls we receive during Georgia's winter months, especially during sudden cold snaps when furnaces that have been idle for months are suddenly called into action.
How Modern Furnace Ignition Works
Most furnaces installed in the last 20 years use electronic ignition rather than a standing pilot light. There are two types:
Hot Surface Ignitor (HSI) — A silicon carbide or silicon nitride element that glows red-hot to ignite the gas. This is the most common type in residential furnaces.
Intermittent Pilot — An electronic spark ignites a small pilot flame, which then ignites the main burners. Less common but still found in many homes.
Common Causes of Ignition Failure
Failed Hot Surface Ignitor — Ignitors are fragile and have a limited lifespan (3–7 years typically). They crack, break, or simply wear out. This is the single most common cause of furnace ignition failure.
Dirty Flame Sensor — The flame sensor detects whether the burners are actually lit. If it's coated with carbon buildup, it can't detect the flame and shuts the gas valve as a safety precaution. The furnace lights briefly, then shuts off.
Gas Supply Issues — A closed gas valve, empty propane tank, or gas line problem will prevent ignition. Check that the gas valve near your furnace is in the "on" position.
Thermostat Problems — If your thermostat isn't sending the "heat" signal to the furnace, the ignition sequence never starts. Check that it's set to "heat" mode and the temperature is set above the current room temperature.
Tripped Safety Switches — Furnaces have multiple safety switches (high-limit, pressure switch, rollout switch) that prevent operation if unsafe conditions are detected. A tripped safety switch prevents ignition.
Control Board Failure — The control board orchestrates the entire ignition sequence. If it fails, the furnace may not initiate the ignition process at all.
What You Can Safely Check
1. Thermostat — Verify it's set to "heat" and the temperature is set high enough
2. Circuit breaker — Make sure the furnace breaker hasn't tripped
3. Gas valve — Confirm the gas valve near the furnace is open
4. Air filter — A severely clogged filter can trigger safety shutdowns
5. Furnace power switch — Check the switch on or near the furnace (looks like a light switch)
What Requires a Professional
Ignitor replacement, flame sensor cleaning, gas valve repair, and control board diagnosis all require a trained technician. Gas furnace repairs involve combustion safety and should never be attempted as DIY projects.
Furnace not igniting? All Seasons provides fast heating repair throughout Carrollton, Bremen, and Tallapoosa. Call (770) 809-1355 for same-day service.