Carrier furnace status code 34 (ignition proving failure) and code 14 (ignition lockout)

By Jason Dearmin · Last reviewed November 14, 2026 · How we check facts

Short answerCode 34 means the furnace tried to light but did not prove a flame. The control repeats the ignition sequence three more times, and then it locks out with code 14, which resets automatically after three hours.

What codes 34 and 14 mean

Carrier's status code list says 34: Ignition proving failure. The control will try three more times before lockout 14 occurs. If the flame signal is lost during the blower on-delay period, the blower comes on for the selected blower-off delay. 14: Ignition lockout auto-resets after three hours.

In plain language: the igniter heated and gas was supplied, but the control could not confirm a flame with the flame sensor, so it shut the gas off for safety.

Carrier's check list for code 34

Oxide buildup on the flame sensor (the technician document says to clean it with fine steel wool)
Proper flame-sense microamps: 0.5 microamps DC minimum, 4.0 to 6.0 nominal
Manual gas valve shut off
Control ground continuity; the green/yellow wire must be connected to the furnace sheet metal
Gas valve defective or gas valve turned off
Low inlet gas pressure
Inadequate flame carryover or rough ignition
Defective hot surface igniter
The flame sensor must not be grounded

What is safe for a homeowner, and what is not

Carrier's consumer page on flame sensors says a dirty or faulty flame sensor is one possible cause when a furnace ignites and then shuts off shortly afterward, and it recommends that a trained HVAC professional clean or replace internal parts like the sensor. Carrier also stresses that a flame sensor is only one possible cause, because ignition, wiring, grounding and gas supply problems can look the same.

The homeowner-level checks are small: make sure the furnace's manual gas shutoff handle is in the open position (handle in line with the pipe) and that other gas appliances work. Do not remove burner or blower doors, test gas pressure or bend or scrape the sensor yourself.

If you smell gas Leave the house immediately, then call your gas utility or 911 from outside. Do not use switches, lighters or phones inside. Carrier tells owners to leave the area and contact the gas utility and an HVAC professional if they smell gas near a furnace.

Related symptoms

If your furnace starts, runs for a few seconds and shuts off, see furnace short cycling. If the igniter glows but burners never light, see igniter glows but no flame.

Frequently asked questions

How many times does the furnace try to light before code 14?

Carrier's table says the control will try three more times after the first failed attempt before ignition lockout 14 occurs. Carrier's consumer guidance adds that the number of attempts varies by model, so check your own furnace documentation.

How do I reset code 14?

Carrier says ignition lockout 14 auto-resets after three hours. The service manual describes other reset steps for technicians; if the code keeps returning, have the furnace serviced instead of resetting repeatedly.

Does code 34 mean the igniter is bad?

Not necessarily. A defective hot surface igniter is on the list, but so are the flame sensor, gas supply, gas valve, grounding and ignition carryover. A technician can measure flame-sense microamps to tell the difference.

Sources

SP05-59 Service and Maintenance Procedures: Deluxe 4-Way Multipoise 2-Stage Direct-Vent Condensing Gas Furnace (Carrier (shareddocs.com)) Covers: Carrier 2-stage condensing gas furnaces with the status-code LED control described in the document. Other Carrier, Bryant and Payne boards can use different codes; check the service label on your furnace.
Furnace Flame Sensor: What It Is, Why It Fails, and How to Fix It (Carrier)

Safety note: this page is general information drawn from the sources above. Gas, combustion and line-voltage repairs belong to a licensed professional. Your own equipment's label and manual take priority over anything here. Read the full disclaimer.