Rheem R96VA0702317MSA Error Code 13: Flame Lost After Established

What Does Code 13 Mean?

Fault code 13 means the Rheem R96V Integrated Furnace Control (IFC) confirmed a flame after a good ignition, then lost that flame signal while the thermostat was still calling for heat. On this two-stage furnace the loss can happen in the first seconds after lighting or partway through a long high- or low-fire run. The IFC logs the event and starts another ignition attempt to restore heat.

A single code 13 is non-critical — the furnace is designed to relight. The problem is repetition. If the flame is lost five times in a row, the control enters a one-hour lockout and alternates code 13 with code 10 (One-Hour Lockout) on the dual 7-segment display, disabling heat until it retries automatically. Code 13 sits between code 12 (Low Flame Sense), the early weak-signal warning, and code 11 (Failed Ignition), where no flame is confirmed at all — so seeing 12 earlier in the season and 13 now points to a flame-sensing problem that is getting worse.

The most common cause is a dirty or weak flame sensor rod that cannot hold a steady sense current once the burners are lit, sometimes combined with a loose sensor wire. Less common are a poorly mounted or poorly grounded sensor, or an unstable flame from burner or seal issues — those are not homeowner repairs. A dirty air filter can also cause the heat exchanger to overheat and trip the limit, which can look like a flame drop-out, so checking the filter is worthwhile. Because the most likely cause is the safe, cleanable one, cleaning the rod (and checking the filter) is the right first step.

What You'll Notice

• The burners light and you feel heat start, then the furnace shuts the flame off before the thermostat is satisfied
• The furnace short-cycles — igniting, running briefly, dropping out, and re-igniting
• The dual 7-segment display shows 13, and alternates 13 with 10 once it has locked out
• After several failed relights the furnace goes quiet for about an hour, then tries again on its own
• Warm air comes in bursts rather than a steady flow during a heat call

Common Causes

How This Is Diagnosed

Because a dirty or weak sensor rod is the usual cause, the logical order is to clean the rod, reseat its wire, and check the air filter first, then watch a full cycle to see whether the flame now holds. If it still drops out, a technician measures the flame-sense current while the burners are lit, checks the sensor mounting and ground, and inspects the burner assembly and gas supply pressure to rule out an unstable flame or a low-pressure condition.

How to Fix It: Clean the Flame Sensor and Check the Air Filter

What You'll Need

• 1/4-inch nut driver or hex driver
• Scotch-Brite pad
• Flashlight
• Replacement air filter (correct size) 🛒 Find at FiltersFast · 🛒 Find at Amazon

Steps

1. Turn off power at the breaker or furnace switch AND shut off the gas supply Switch the furnace circuit breaker (or the service switch on the furnace) to OFF, then turn the manual gas shutoff valve perpendicular to the pipe. If you smell gas, leave immediately and call your gas company.
2. Locate and remove the flame sensor Remove the burner-compartment access panel. The flame sensor is a single thin metal rod with a white porcelain base and one wire, mounted at the far end of the burner assembly opposite the igniter. Unplug the wire, remove the single 1/4-inch mounting screw, and slide the rod out, holding it by the porcelain base.
3. Clean the rod Gently clean the flame sensor rod with a Scotch-Brite pad until the metal is dull-bright. Rheem'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. If the porcelain is cracked, the rod needs replacement rather than cleaning.
4. Reinstall the sensor and reseat the wire Slide the rod back so it will sit in the burner flame path, tighten the screw snugly, and push the wire connector fully onto the sensor terminal so it cannot vibrate loose.
5. Check the air filter Inspect the furnace air filter. If it is gray, clogged, or you cannot see light through it, replace it with the correct size. Restricted airflow can overheat the heat exchanger and cause a shutdown that mimics flame loss.
6. Restore gas and power, then test Return the manual gas valve to the open position (handle parallel to the pipe) and switch power back on. If the furnace is in the one-hour lockout (alternating 13 and 10), cut power for 30 seconds to clear it, then call for heat and watch a full cycle.

When to Call a Professional

Contact a licensed HVAC technician if:

• The flame keeps dropping out mid-cycle after the sensor is cleaned and the wire reseated
• The furnace has reached the one-hour lockout (alternating 13 and 10) and code 13 returns after it clears
• The burner flame looks yellow, soft, or unsteady, or appears to lift off the burner ports
• You suspect low or fluctuating gas pressure, which requires a technician with a manometer to measure supply and manifold pressure
• Code 13 follows a run of code 12 events earlier in the season, indicating progressive sensor degradation that cleaning alone will not fix

✓ Verified against manufacturer service manual — March 2026