Ruud U96VA0702317MSA Error Code 11: Failed Ignition
What Does Code 11 Mean?
Code 11 on the Ruud U96VA0702317MSA appears after a failed ignition attempt. During a normal cycle the inducer establishes draft, the hot-surface igniter glows, the gas valve opens, and the flame sensor confirms a flame. When the control cannot confirm flame, it registers code 11, runs a 20-second post-purge, and tries again. This repeats until gas heat is established or until four consecutive failures occur, at which point the fault escalates to a one-hour lockout (code 10, alternating with 11).
The most common cause is a dirty flame-sense rod that can no longer detect the flame even when the burners light — the same rod involved in the related low-flame-sense warning (code 12) and flame-loss fault (code 13). Other causes include a gas valve that was left turned off, a weak or mispositioned hot-surface igniter, or flame that does not carry across all burners.
Because cleaning the flame sensor is a recognized homeowner-safe task, that is the one repair covered below. Igniter, gas-valve, and control-board issues are not DIY and should go to a technician.
What You'll Notice
- The inducer runs and the igniter glows, but the burners do not stay lit
- The furnace tries several times, then shows 11 alternating with 10 and stops heating for an hour
- You feel little or no warm air even though the furnace is clearly attempting to start
- You may hear the ignition sequence repeat every few minutes
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Dirty flame sense rod | Most common | ✓ DIY fix → |
| Gas valve turned off | Common | ✓ DIY fix → |
| Faulty or mispositioned igniter | Common | ✗ Call a pro → |
How This Is Diagnosed
Start with the simplest checks: confirm the manual gas shutoff valve is on, then inspect the flame-sense rod for dark oxide buildup, since a dirty rod is the most common cause. If cleaning the rod does not restore reliable ignition, the igniter, gas supply/valve, and manifold pressure are checked next — that is technician territory.
How to Fix It: Clean the Flame Sensor
What You'll Need
Steps
- Turn off power at the breaker or switch and shut off the gas supply Switch off the furnace at its dedicated breaker or the service switch on the unit, then turn the manual gas shutoff valve near the furnace to the OFF position (handle crosswise to the pipe). If you smell gas, leave immediately and call your gas company. Give the unit a minute for the inducer to stop before opening any panels.
- Open the burner-compartment access panel Remove the furnace front/burner access panel to expose the burner assembly. On the U96VA the panel is held by screws or clips; set it and any fasteners aside safely.
- Locate and remove the flame sensor The flame sensor is a thin metal rod with a white porcelain base mounted at the end of the burner assembly, with a single wire attached. Note its orientation, unplug the wire, and remove the mounting screw so you can lift the rod out.
- Clean the flame sensor rod Gently clean the flame sensor rod with a Scotch-Brite pad until the metal is dull-bright. Ruud's guide lists fine steel wool as the cleaning material, but many HVAC technicians prefer a Scotch-Brite pad because it leaves no abrasive residue on the rod. Do not clean or scratch the white porcelain base, and take care not to bend the rod.
- Reinstall the sensor and confirm the gas valve is on Refit the rod in its bracket in the same orientation, tighten the mounting screw, and reconnect the wire so the tip will sit in the flame path. Verify the manual gas shutoff valve is back in the ON position (handle in line with the pipe).
- Restore gas and power, then test Reopen the gas supply, switch power back on, and set the thermostat to call for heat. Watch a full ignition cycle. The control may need a power cycle (off ~30 seconds, then on) to clear the stored code.
When to Call a Professional
Contact a licensed HVAC technician if:
- Ignition still fails after the flame sensor has been cleaned
- The hot-surface igniter does not glow during the ignition sequence
- You hear gas but the burners will not light — stop and do not troubleshoot the gas valve yourself
- The fault repeatedly escalates to a one-hour lockout (code 10)
Frequently Asked Questions
How many times will the Ruud U96VA try to ignite before locking out?
It makes four consecutive attempts, each followed by a post-purge; after the fourth failure it enters a one-hour lockout and alternates code 10 with code 11.
Will cleaning the flame sensor fix code 11?
Often yes, because a dirty flame-sense rod is the most common cause; if ignition still fails afterward, the igniter, gas supply, or control likely needs a technician.
How much does it cost to fix code 11 if it is not the flame sensor?
It depends on the actual part — an igniter is far cheaper than a gas valve or control board — and prices vary by region, so get a local quote once a technician identifies the cause.
✓ Verified against manufacturer service manual — March 2026