Clean or replace furnace flame sensor
Why it matters
A failed or dirty flame sensor is the #1 cause of furnace short-cycling (burner lights then shuts off immediately), leaving homeowners without heat during cold weather.
Stop forgetting to do this.
Hearth generates a personalized maintenance schedule so you never miss another clean or replace furnace flame sensor.
How to do it
- 1
Turn off the furnace at the circuit breaker and allow it to cool for 5 minutes.
- 2
Open the furnace access panel to expose the burner assembly and controls.
- 3
Locate the flame sensor rod (thin ceramic rod near the burner flame area).
- 4
Gently pull the rod straight out of its bracket or holder.
- 5
Inspect the rod for black carbon buildup or corrosion on the surface.
- 6
Clean the rod gently with fine steel wool or soft cloth if soiled.
- 7
Reinsert the rod carefully, ensuring it points into the burner flame zone.
- 8
Close the access panel and restore power to test furnace ignition.