Carrier 59SC2B Error Code 14: Ignition Lockout
What Does Code 14 Mean?
Status code 14 on the Carrier 59SC2B indicates an ignition lockout. The furnace attempted to ignite multiple times but could not confirm a flame, so it has shut down for safety. The control will automatically try to reset after 3 hours.
During a normal heating cycle, the inducer motor starts, the hot surface igniter glows, the gas valve opens, and the flame sensor verifies that combustion is occurring. If the flame sensor cannot detect a flame — even if gas is actually burning — the control board shuts off the gas valve. After several failed attempts (see code 34), the furnace enters this lockout state.
The most common cause is a dirty flame sensor with oxide buildup that prevents it from detecting the flame properly. The flame sensor works by measuring a tiny electrical current (microamps) through the flame. When coated with oxidation, this current drops below the minimum threshold. The second most common cause is the gas supply being turned off. A defective hot surface igniter or low gas pressure are also possible causes but typically require professional diagnosis.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Dirty flame sensor | Most common | ✓ DIY fix → |
| Gas supply turned off or low gas pressure | Common | ✓ DIY fix → |
| Defective hot surface igniter | Common | ✗ Call a pro → |
How to Fix It: Clean the Flame Sensor and Check Gas Supply
What You'll Need
Steps
- Turn off electrical power at the breaker and shut off the gas supply valve Locate the furnace circuit breaker and flip it to OFF. Turn the gas shutoff valve to the OFF position (perpendicular to the pipe). If you smell gas, leave immediately and call your gas company.
- Locate the flame sensor Open the furnace access panel and look near the burner assembly. The flame sensor is a thin metal rod (usually bent at an angle) mounted with a porcelain insulator. It typically has a single wire connected to it and is held in place by one 1/4-inch screw.
- Remove the flame sensor Disconnect the wire from the flame sensor. Remove the mounting screw and carefully pull the sensor out. Handle it by the porcelain insulator or mounting bracket, not the rod itself.
- Clean the sensor rod Gently rub the metal rod with a Scotch-Brite pad until it is clean and shiny, removing all oxide buildup. Do not bend the rod or damage the porcelain insulator.
- Reinstall the flame sensor Place the sensor back in its bracket, secure the mounting screw, and reconnect the wire. Ensure the sensor rod will be positioned in the flame path when the burners ignite. The green/yellow wire must be connected to the furnace sheet metal for proper ground continuity.
- Verify the gas supply is on Check that the manual gas shutoff valve near the furnace is open (handle parallel to the pipe). Also verify the gas meter valve is open if accessible.
- Restore power and gas, then test Turn the gas supply valve to ON and flip the circuit breaker to ON. Set your thermostat to call for heat and watch the ignition sequence. The furnace may need a power cycle to clear the lockout (turn off for 30 seconds, then back on).
When to Call a Professional
Contact a licensed HVAC technician if:
- The burners still fail to stay lit after cleaning the flame sensor
- The hot surface igniter does not glow during the ignition sequence
- You can hear gas flowing but it does not ignite
- The flame appears yellow, lazy, or rolls out of the combustion chamber
- Code 14 occurs repeatedly even with a clean flame sensor and open gas supply
✓ Verified against manufacturer service manual — March 2026