York TM9T100C16MP11 Error Code Ignition Failure (3 Failed Attempts): Ignition Failure (3 Failed Attempts)

What Does Code Ignition Failure (3 Failed Attempts) Mean?

When the S1-33103010000 control board in your York furnace displays 7 red flashes, it means the furnace attempted to ignite 3 times (3 trials for ignition) and failed each time. The board has entered a 1-hour soft lockout as a safety precaution. After the lockout period, the furnace will automatically retry, or you can reset it immediately by cycling power off for 30 seconds.

During each ignition attempt, the board runs the inducer motor, confirms the pressure switch closes, heats the hot surface igniter, and opens the gas valve. The flame sensor then has a few seconds to detect flame. If it does not register sufficient microamp current, the board closes the gas valve and counts it as a failed attempt. After the third failure, the 7-red-flash lockout activates.

There are two common causes: either the flame sensor is dirty and cannot detect the flame even though the burner is lit, or the hot surface igniter is weak and not getting hot enough to ignite the gas. Flame sensor cleaning is the most frequent fix and is a straightforward DIY task.

How to Fix It: Clean the Flame Sensor on Your York Furnace

What You'll Need

• 1/4-inch hex-head driver or nut driver
• Fine-grit emery cloth or Scotch-Brite pad
• Clean dry cloth or paper towel

Steps

1. Turn off power AND shut off gas supply Turn off the furnace power switch (typically located on or near the furnace). Locate the gas shutoff valve on the supply pipe and turn it to OFF (perpendicular to the pipe). Wait 5 minutes before proceeding. If you smell gas at any point, leave the area immediately and call your gas company.
2. Remove the access panels Remove the lower and upper access panels on your York furnace. The LED is visible through the lower door viewport, and the burner compartment is accessible behind the upper panel.
3. Locate the flame sensor The flame sensor on York furnaces is a thin metal rod mounted on the burner assembly with a single screw. It has one wire attached to it. It is positioned so the rod extends into the flame path of one of the burners, usually on the opposite end from the hot surface igniter.
4. Remove the flame sensor Pull the wire connector straight off the flame sensor terminal. Remove the single 1/4-inch mounting screw and slide the sensor out.
5. Clean the sensor rod Use fine-grit emery cloth or a Scotch-Brite pad to gently clean the metal rod. Remove all oxidation and buildup until the rod is shiny. Do NOT use steel wool, as steel particles can embed in the sensor. Do NOT bend the rod. Wipe clean with a dry cloth.
6. Reinstall the flame sensor Reinsert the sensor into its mounting position, secure the screw, and reconnect the wire connector firmly.
7. Restore power and gas, then test Replace the access panels. Turn the gas supply back ON (parallel to the pipe). Restore furnace power. Set your thermostat to call for heat. Watch the LED through the viewport on the lower access panel.

When to Call a Professional

Contact a licensed HVAC technician if:

• The 7-red-flash code returns after cleaning the flame sensor
• The igniter does not glow orange/white during the ignition sequence
• The gas valve clicks but no flame appears at the burners
• The burner lights but the flame goes out within a few seconds
• You smell gas at any point