Status LED flashes once repeatedly, furnace will not start heating cycle

Safety first: Turn off power to the furnace at the service switch and shut off the gas supply before removing panels. If you smell gas continuously, evacuate and contact your gas utility or a licensed technician immediately.

Steps to check:

• Verify thermostat call for heat: Set thermostat to HEAT and raise the setpoint 5°F above room temperature. Confirm the thermostat is powered and set to the correct mode.
• Check gas supply: Ensure the manual gas shutoff valve near the Trane furnace gas train is parallel to the pipe (open). Confirm other gas appliances in the home work.
• Inspect hot surface ignitor: Remove the burner access panel. Locate the silicon carbide or silicon nitride hot surface ignitor near the burners. Look for cracks, white spots, or breaks. Do not touch the element with bare fingers.
• Clean flame sensor: Locate the flame sensor rod (usually a single rod in front of a burner). Remove the mounting screw, gently clean the rod with fine steel wool or emery cloth, wipe with a clean dry cloth, and reinstall.
• Reset power: Restore power and gas, then cycle the furnace. Watch through the sight glass: inducer starts, ignitor glows, gas valve clicks, burners light. If ignitor never glows or burners never light, the ignitor or gas valve may be faulty.

When to call a professional: If the ignitor does not glow, if you see repeated ignition attempts with no flame, or if you are not comfortable working around gas components, contact a qualified Trane service technician.