Ruud U96VA0702317MSA Error Code 13: Flame Lost After Established

What Does Code 13 Mean?

Code 13 on the Ruud U96VA0702317MSA means the burners lit and the flame was properly sensed, but then the Integrated Furnace Control stopped sensing flame during the heat call. The control immediately shows 13 and attempts to relight. This is not critical on its own, but if flame is lost five times in a row the furnace enters a one-hour lockout, alternating code 13 with code 10.

Code 13 sits in the middle of the flame-sensing progression on this board: a weak signal shows as code 12, actual loss of an established flame shows as code 13, and inability to prove flame at startup shows as code 11. All three most often trace back to the same flame-sense rod.

The most common cause is a dirty flame-sense rod or a poor wiring connection between the rod and the control. An unstable flame pattern — from burner or combustion-seal problems — can also cause repeated dropouts. Cleaning the rod is homeowner-safe; inspecting the burner assembly and combustion-door seals is technician work.

What You'll Notice

• The burners light, then go out a short time later, and the furnace tries to relight
• Heating is short-cycling — brief bursts of warm air that do not last
• After repeated losses the display alternates 13 with 10 and heat stops for an hour
• Cooling and fan continue to work normally

Common Causes

How This Is Diagnosed

Since a dirty flame-sense rod or poor connection is the most common cause, the rod is cleaned and its wiring and ground checked first. If the flame still drops out, the technician looks at flame stability — inspecting the burner assembly, the seals between the burner and blower compartments, and the combustion-door gasket, since an unstable flame pattern can also cause loss after ignition.

How to Fix It: Clean the Flame Sensor

What You'll Need

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

Steps

1. 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.
2. Open the burner-compartment access panel Remove the furnace front/burner access panel to expose the burner assembly, keeping the panel and fasteners together.
3. Locate and remove the flame sensor Identify the thin metal rod with a white porcelain base at the end of the burner assembly. Note its orientation, unplug the single wire, and remove the mounting screw to lift the rod out.
4. 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.
5. Reinstall the sensor and check its wire Refit the rod in the same orientation, tighten the mounting screw, and reconnect the wire, making sure the connection is snug and the sensor is firmly grounded to its bracket.
6. Restore gas and power, then test Reopen the gas supply, restore power, and call for heat. A power cycle (off ~30 seconds, then on) may be needed to clear the stored code.

When to Call a Professional

Contact a licensed HVAC technician if:

• Flame is still lost after the sensor has been cleaned and its wiring checked
• The furnace reaches a one-hour lockout with code 13 alternating with code 10
• The flame looks unstable or you suspect a burner or combustion-door seal problem

✓ Verified against manufacturer service manual — March 2026