Carrier 59SC2B Error Code 14: Ignition Lockout

What Does Code 14 Mean?

Status code 14 (one short flash, four long flashes) on the Carrier 59SC2B is an ignition lockout. It is the terminal state of the ignition-proving sequence: after the control fails to confirm a flame across its retries (reported live as code 34), it shuts the furnace down and auto-resets only after about 3 hours.

On each attempt the HK42FZ034-type board runs the inducer, energizes the hot surface igniter, opens the gas valve, and then looks to the flame sensor to confirm combustion. The flame sensor proves flame by passing a tiny microamp current through the flame to ground. If that current is not seen — even when gas is actually burning — the board closes the gas valve for safety. Enough of those failures in a row produces this lockout.

The most common reason the current goes missing is a flame sensor coated in oxide, which insulates the rod and drops the signal below threshold. The next most common is simply that the gas supply is off. A weak or failed hot surface igniter and low gas pressure are also possible but call for professional diagnosis. Because code 14 shares its root causes with code 34, cleaning the sensor and confirming gas usually resolves both.

What You'll Notice

• The furnace tries to light several times, then stops attempting and stays off (locked out)
• You hear the inducer and see the igniter glow, gas lights briefly, then the flame drops out within a second or two
• No heat despite the thermostat calling; the lockout clears after about 3 hours and may repeat
• Code recall shows a one-short, four-long pattern, often preceded by code 34

Common Causes

How This Is Diagnosed

The sequence is checked in the order it happens: is there ignition at all, and does the flame stay proven? A dirty flame sensor (the most common cause) is cleaned and the gas supply confirmed open first. If the burners still will not stay lit, attention moves to whether the igniter glows, whether gas is reaching the burners at proper pressure, and whether the sensor's ground path (the green/yellow wire to sheet metal) is intact — the latter checks being technician territory.

How to Fix It: Clean the Flame Sensor and Confirm the Gas Supply

What You'll Need

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

Steps

1. Turn off power at the breaker and shut off the gas supply valve Flip the furnace circuit breaker to OFF and turn the manual gas shutoff valve to the OFF position (perpendicular to the pipe). If you smell gas, leave immediately and call your gas company.
2. Locate the flame sensor Open the furnace access panel and look at the burner assembly. The flame sensor is a thin metal rod, usually bent, mounted on a white porcelain base with a single wire, held by one 1/4-inch screw.
3. Remove the flame sensor Disconnect the wire, remove the mounting screw, and carefully withdraw the sensor. Handle it by the porcelain base or bracket, never by the rod.
4. Clean the sensor rod Gently clean the flame sensor rod with a Scotch-Brite pad until the metal is dull-bright. Carrier'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 flame sensor Set the sensor back in its bracket, secure the screw, and reconnect the wire so the rod sits in the flame path. Confirm the green/yellow ground wire is connected to the furnace sheet metal, as the sensor must not be left ungrounded.
6. Confirm the gas supply is on Check that the manual gas shutoff valve at the furnace is open (handle parallel to the pipe), and that the meter valve is open if accessible.
7. Restore gas and power, then test Turn the gas valve to ON and the breaker to ON. Because this is a lockout, you may need to cycle power once (off 30 seconds, then on) to clear code 14. Set the thermostat to call for heat and watch the ignition sequence.

When to Call a Professional

Contact a licensed HVAC technician if:

• The burners still fail to stay lit after cleaning the flame sensor and confirming gas is on
• The hot surface igniter does not glow during the ignition sequence
• You can hear gas but it never ignites
• The flame looks yellow, lazy, or lifts and rolls out of the burners
• Code 14 keeps returning despite a clean sensor and open gas supply

✓ Verified against manufacturer service manual — March 2026