Ruud U96VA0702317MSA Error Code 11: Failed Ignition

What Does Code 11 Mean?

Code 11 on the Ruud U96VA0702317MSA indicates a failed ignition attempt. The furnace control detected that combustion did not occur during the ignition sequence. The system will continue to display this code while retrying — if it fails to ignite four consecutive times, the fault escalates to code 10 (ignition lockout) and the furnace shuts down.

During a normal heating cycle, the inducer motor starts to establish draft, the hot surface igniter heats up, and the gas valve opens. The flame sensor then checks for the presence of a flame. If the sensor cannot confirm combustion — either because no flame exists or because the sensor is too dirty to detect one — the control board closes the gas valve and registers the fault.

The most common cause is oxide buildup on the flame sensor rod, which insulates it from properly sensing the flame current. Other possible causes include a closed gas supply valve, a weak or cracked hot surface igniter, or a clogged condensate drain preventing the inducer from establishing proper draft. If the issue is a dirty flame sensor, cleaning it is a straightforward DIY task.

Common Causes

How to Fix It: Clean the Flame Sensor

What You'll Need

• 1/4-inch nut driver or hex head driver
• Scotch-Brite pad
• Flashlight

Steps

1. Turn off power at the breaker and shut off the gas supply valve Locate the furnace circuit breaker and flip it to OFF. Turn the manual gas shutoff valve near the furnace to the OFF position (perpendicular to the pipe). If you smell gas at any point, leave the house immediately and call your gas company from outside.
2. Open the furnace access panel Remove the front access panel on the furnace to expose the burner assembly. On the U96VA, the panel may be secured with screws or clips. Set it aside in a safe place.
3. Locate and remove the flame sensor The flame sensor is a thin metal rod with a porcelain insulator, mounted near the burner assembly with a single screw. It has one wire connected to it. Disconnect the wire and remove the mounting screw, then carefully pull the sensor out.
4. Clean the sensor rod Gently rub the metal rod with a Scotch-Brite pad until all dark oxide buildup is removed and the rod appears clean and shiny. Do not use steel wool, as it can leave residue. Avoid bending the rod or damaging the porcelain insulator.
5. Reinstall the flame sensor Place the sensor back in its bracket, tighten the mounting screw, and reconnect the wire. Make sure the rod will be positioned in the flame path when the burners ignite.
6. Check the gas supply and condensate drain Verify the manual gas shutoff valve is open (handle parallel to the pipe). Also check that the condensate drain line is not clogged — a blocked drain can prevent proper inducer operation on high-efficiency furnaces like the U96VA.
7. Restore power and gas, then test Turn the gas supply valve to ON and flip the circuit breaker back to ON. Set your thermostat to call for heat and observe the ignition sequence. The furnace may need a power cycle (off for 30 seconds, then on) to clear the fault code.

When to Call a Professional

Contact a licensed HVAC technician if:

• The furnace still fails to ignite after cleaning the flame sensor
• The hot surface igniter does not glow during the ignition sequence
• You hear gas flowing but it does not ignite — do not attempt further troubleshooting
• The fault escalates to code 10 (ignition lockout) repeatedly
• The condensate drain appears clear but the inducer still does not operate correctly

✓ Verified against manufacturer service manual — March 2026