Ruud U802VA050317MSA Error Code T013_F: Flame Lost after Established (Transient)
What Does Code T013_F Mean?
Code T013_F on the Ruud U802VA indicates that the burner flame was established but then lost during a heating cycle. The 'T' prefix means this is a transient (intermittent) fault — it happened at least once but may not be happening continuously. If flame is lost five times during a single heat call, the furnace escalates to a one-hour lockout (code A114_F).
When the furnace is running, the flame sensor continuously monitors the burner flame by detecting a small electrical current through the flame. If the sensor is coated with oxidation or carbon buildup, it may intermittently fail to detect the flame, causing the control board to shut off the gas valve as a safety precaution.
While a dirty flame sensor is the most common cause, intermittent gas supply fluctuations or strong drafts in the combustion area can also cause the flame to go out. If this code appears only occasionally and the furnace recovers on its own, the flame sensor is the most likely culprit.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Dirty flame sensor | Most common | ✓ DIY fix → |
| Intermittent gas supply issue | Common | ✗ Call a pro → |
How to Fix It: Clean the Flame Sensor
What You'll Need
Steps
- Turn off electrical power at the breaker or power switch AND shut off the gas supply valve Locate the furnace circuit breaker and flip it to OFF, or use the power switch on or near the furnace. Turn the gas shutoff valve to the OFF position (perpendicular to the pipe). If you smell gas at any point, leave the area immediately and call your gas company.
- Open the furnace access panel and locate the flame sensor Remove the furnace's front access panel. The flame sensor is a thin metal rod with a porcelain insulator base, mounted near the burners. It extends into the burner flame path and is held by a single mounting screw.
- Remove and clean the flame sensor Disconnect the wire connector from the sensor and remove the mounting screw. Gently rub the metal rod with a Scotch-Brite pad until it is clean and shiny. Do not use steel wool, as it can leave metal fibers on the porcelain insulator. Wipe clean with a cloth.
- Reinstall the flame sensor and close the panel Reattach the flame sensor with the mounting screw and reconnect the wire connector. Ensure the rod is properly positioned in the burner flame path. Replace the access panel.
- Restore gas and power, then test Turn the gas supply valve to ON (parallel to the pipe) and restore electrical power. Set the thermostat to call for heat. Monitor the furnace through several complete heating cycles to confirm the flame stays lit throughout.
When to Call a Professional
Contact a licensed HVAC technician if:
- Code T013_F continues to appear after cleaning the flame sensor
- The flame visibly flickers or appears unsteady during operation
- You notice a yellow or orange flame instead of a steady blue flame
- The furnace escalates to code A013_F or A114_F (persistent flame loss)
- You suspect a gas supply issue (other gas appliances also having problems)
Sources
✓ Verified against manufacturer service manual — March 2026