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Carrier gas furnace code 34: Flame not proved during ignition

Gas furnace, Canada and United States

The burners did not light, or the control did not sense their flame, during the ignition trial. The control tries again, and after its last try it locks out with code 14. If the flame is lost during the blower on-delay, the blower runs for its off-delay.

On the status light, this code is 3 short flashes, then 4 long flashes.

This needs a licensed gas technician. There are a few safe checks you can do first, marked below. Anything inside the unit is a job for a professional.

This involves the gas supply or burner. Only a licensed technician should open the unit or work on gas parts.

What causes it

Standard amber-LED furnaces

  1. The gas is off, with the manual shut-off valve to the furnace closed or the control switch on the gas valve turned off.

    Check the gas is turned on to the furnaceYou can do this

    1. Check the manual shut-off valve in the gas pipe leading to the furnace is open.
    2. If the control switch on the furnace's gas valve may be off, use the start-up steps in the owner's manual or on the inside of the main furnace door. Set the thermostat to its lowest setting and OFF, close the manual gas valve, turn off the power and remove the main furnace door.
    3. Turn the control switch on the gas valve to OFF and wait five minutes, then smell for gas, including near the floor.
      If you smell gas, stop. Do not light any appliance or touch electrical switches. Leave the building and call your gas supplier from a neighbor's phone.
    4. If there is no gas smell, turn the control switch to ON, refit the main door, turn the power on and wait one minute, open the manual gas valve, then set the thermostat to HEAT above the room temperature.
    5. If the burners do not light, or the furnace locks out, shut the furnace down and call your dealer.

    Book a licensed gas technician

  2. A dirty flame sensor (oxide build-up) or a flame sensing current that is too low.

    Book a licensed gas technician

  3. Low inlet gas pressure, poor flame carryover or rough ignition, or a faulty hot surface igniter.

    Book a licensed gas technician

  4. A grounding problem, such as the green/yellow wire not connected to the furnace sheet metal, poor control ground continuity, or a grounded flame sensor.

    Book a licensed gas technician

  5. A faulty gas valve that does not open when it is powered.

    Book a licensed gas technician

Ultra-low NOx furnaces

  1. The gas is off, with the manual shut-off valve to the furnace closed or the control switch on the gas valve turned off.

    Same check as above: Check the gas is turned on to the furnace

    Book a licensed gas technician

  2. A dirty flame sensor (oxide build-up) or a flame sensing current that is too low.

    Book a licensed gas technician

  3. Low inlet gas pressure, poor flame carryover or rough ignition, or a faulty gas valve.

    Book a licensed gas technician

  4. A grounding problem, such as the green/yellow wire not connected to the furnace sheet metal, poor control ground continuity, or a flame sensor that is grounded or touching the casing.

    Book a licensed gas technician

How to read this code on your unit

The amber status light (red on some older boards) on the furnace control shows through a small window in the blower access door. A steady light means the control has power and no fault to show. A code is two digits. Count the short flashes for the first digit, then the long flashes for the second, so 3 short flashes followed by 3 long flashes is code 33, and 1 short then 1 long is code 11. Write the code down before you open the door or switch the furnace off.

Booking a licensed gas technician

Book a licensed gas technicianlicensed gas technician

  1. Turn the unit off and leave the covers on. Gas components must only be serviced by a licensed technician.
  2. Note the code, how often it appears, and the model and serial numbers from the rating label.
  3. Book a licensed gas technician and give them those details.

Models that show this code

328 models in 26 ranges
RangeModels
58CTA/CTX58CTA045-08, 58CTA045-12, 58CTA070-08, 58CTA070-12, 58CTA070-16, 58CTA090-14, 58CTA090-16, 58CTA090-20, 58CTA110-12, 58CTA110-16, 58CTA110-22, 58CTA135-16, 58CTA135-22, 58CTA155-20, 58CTX045-08, 58CTX045-12, 58CTX070-08, 58CTX070-12, 58CTX070-16, 58CTX090-14, 58CTX090-16, 58CTX090-20, 58CTX110-12, 58CTX110-16, 58CTX110-22, 58CTX135-16, 58CTX135-22, 58CTX155-20
58CVA/CVX58CVA070-12, 58CVA090-16, 58CVA110-20, 58CVA135-22, 58CVA155-22, 58CVX070-12, 58CVX090-16, 58CVX110-20, 58CVX135-22, 58CVX155-22
58DLA/DLX58DLA045-08, 58DLA045-12, 58DLA070-08, 58DLA070-12, 58DLA070-16, 58DLA090-14, 58DLA090-16, 58DLA090-20, 58DLA110-12, 58DLA110-16, 58DLA110-22, 58DLA135-16, 58DLA135-22, 58DLA155-20, 58DLX045-08, 58DLX045-12, 58DLX070-08, 58DLX070-12, 58DLX070-16, 58DLX090-14, 58DLX090-16, 58DLX090-20, 58DLX110-12, 58DLX110-16, 58DLX110-22, 58DLX135-16, 58DLX135-22, 58DLX155-20
58SB0A/58SB1A58SB0A045E14-12, 58SB0A045E17-12, 58SB0A070E14-12, 58SB0A070E17-12, 58SB0A070E17-16, 58SB0A070E21-16, 58SB0A090E17-14, 58SB0A090E21-16, 58SB0A090E21-20, 58SB0A090E24-20, 58SB0A110E21-20, 58SB0A110E24-20, 58SB0A135E24-20, 58SB0A155E24-20, 58SB1A045E14-12, 58SB1A045E17-12, 58SB1A070E14-12, 58SB1A070E17-12, 58SB1A070E17-16, 58SB1A070E21-16, 58SB1A090E17-14, 58SB1A090E21-16, 58SB1A090E21-20, 58SB1A090E24-20, 58SB1A110E21-20, 58SB1A110E24-20, 58SB1A135E24-20, 58SB1A155E24-20
58SC0A/58SC1A58SC0A045E14-12, 58SC0A045E17-12, 58SC0A070E14-12, 58SC0A070E17-12, 58SC0A070E17-16, 58SC0A070E21-16, 58SC0A090E17-14, 58SC0A090E21-16, 58SC0A090E21-20, 58SC0A090E24-20, 58SC0A110E21-20, 58SC0A110E24-20, 58SC0A135E24-20, 58SC1A045E14-12, 58SC1A045E17-12, 58SC1A070E14-12, 58SC1A070E17-12, 58SC1A070E17-16, 58SC1A070E21-16, 58SC1A090E17-14, 58SC1A090E21-16, 58SC1A090E21-20, 58SC1A090E24-20, 58SC1A110E21-20, 58SC1A110E24-20, 58SC1A135E24-20
58SP0A/58SP1A58SP0A045V14-12, 58SP0A045V17-16, 58SP0A070V17-16, 58SP0A070V21-20, 58SP0A090V21-20, 58SP0A090V24-20, 58SP0A110V24-22, 58SP1A045V14-12, 58SP1A045V17-16, 58SP1A070V17-16, 58SP1A070V21-20, 58SP1A090V21-20, 58SP1A090V24-20, 58SP1A110V24-22
58STA/STX58STA045-08, 58STA045-12, 58STA070-08, 58STA070-12, 58STA070-16, 58STA090-14, 58STA090-16, 58STA090-20, 58STA110-12, 58STA110-16, 58STA110-22, 58STA135-16, 58STA135-22, 58STA155-20, 58STX045-08, 58STX045-12, 58STX070-08, 58STX070-12, 58STX070-16, 58STX090-14, 58STX090-16, 58STX090-20, 58STX110-12, 58STX110-16, 58STX110-22, 58STX135-16, 58STX135-22, 58STX155-20
58TN0A/58TN1A58TN0A045C17-12, 58TN0A070C14-12, 58TN0A070C17-16, 58TN0A070C21-20, 58TN0A090C17-16, 58TN0A090C21-20, 58TN0A110C21-20, 58TN0A135C24-22, 58TN1A045C17-12, 58TN1A070C14-12, 58TN1A070C17-16, 58TN1A070C21-20, 58TN1A090C17-16, 58TN1A090C21-20, 58TN1A110C21-20, 58TN1A135C24-22
58TP0A/58TP1A58TP0A045V14-12, 58TP0A070V14-12, 58TP0A070V17-16, 58TP0A090V17-16, 58TP0A090V21-20, 58TP0A110V21-22, 58TP0A135V24-22, 58TP1A045V14-12, 58TP1A070V14-12, 58TP1A070V17-16, 58TP1A090V17-16, 58TP1A090V21-20, 58TP1A110V21-22, 58TP1A135V24-22
59MN7A59MN7A060V17-14, 59MN7A080V17-14, 59MN7A060V21-20, 59MN7A080V21-20, 59MN7A100V21-22, 59MN7A120V24-22
59MN7B59MN7B060C17-14, 59MN7B060C21-20, 59MN7B080C17-14, 59MN7B080C21-20, 59MN7B100C21-22, 59MN7B120C24-22
59SC2A, 59SC2B and 59SC2C59SC2A040E14-10, 59SC2A060E14-10, 59SC2A060E17-14, 59SC2A080E17-16, 59SC2A080E21-20, 59SC2A100E21-14, 59SC2A100E21-20, 59SC2A120E24-20, 59SC2B040E14-10, 59SC2B060E14-12, 59SC2B040E17-12, 59SC2B060E17-16, 59SC2B080E17-16, 59SC2B080E21-20, 59SC2B100E21-16, 59SC2B100E21-22, 59SC2B120E24-22, 59SC2C040E14-10, 59SC2C060E14-12, 59SC2C040E17-12, 59SC2C060E17-16, 59SC2C080E17-16, 59SC2C080E21-20, 59SC2C100E21-16, 59SC2C100E21-20, 59SC2C120E24-20
59SC2D59SC2D040E14-10, 59SC2D040E17-12, 59SC2D060E14-12, 59SC2D060E17-14, 59SC2D080E17-16, 59SC2D080E21-20, 59SC2D100E21-20, 59SC2D100E21-22, 59SC2D120E24-20
59SC5A59SC5A026E14-08, 59SC5A040E14-10, 59SC5A060E14-10, 59SC5A040E17-12, 59SC5A060E17-14, 59SC5A080E17-16, 59SC5A080E21-20, 59SC5A100E21-14, 59SC5A100E21-20, 59SC5A120E24-20, 59SC5A140E24-20
59SC5B59SC5B026E14-10, 59SC5B040E14-10, 59SC5B040E17-12, 59SC5B060E14-12, 59SC5B060E17-16, 59SC5B080E17-16, 59SC5B080E21-20, 59SC5B100E21-20, 59SC5B100E21-22, 59SC5B120E24-22, 59SC5B140E24-22
59SP5A59SP5A026E14-10, 59SP5A040E14-10, 59SP5A060E14-12, 59SP5A040E17-12, 59SP5A060E17-14, 59SP5A080E17-16, 59SP5A080E21-20, 59SP5A100E21-20, 59SP5A120E24-22
59SP6A59SP6A040V14-10, 59SP6A040V17-12, 59SP6A060V14-12, 59SP6A060V17-14, 59SP6A080V17-16, 59SP6A080V21-20, 59SP6A100V21-20, 59SP6A120V24-22
59TN6A59TN6A060V17-14, 59TN6A080V17-14, 59TN6A080V21-20, 59TN6A100V21-22, 59TN6A120V24-22
59TN6B59TN6B060C17-14, 59TN6B080C17-14, 59TN6B080C21-20, 59TN6B100C21-22, 59TN6B120C24-22
59TP5A59TP5A040E14-10, 59TP5A060E14-12, 59TP5A040E17-12, 59TP5A060E17-14, 59TP5A080E17-16, 59TP5A080E21-20, 59TP5A100E21-20, 59TP5A120E24-22
59TP6A59TP6A040V14-10, 59TP6A040V14-12, 59TP6A060V17-12, 59TP6A060V17-14, 59TP6A080V17-16, 59TP6A080V21-20, 59TP6A100V21-20, 59TP6A120V24-22
59TP6B59TP6B040V14-10, 59TP6B040V17-12, 59TP6B060V14-12, 59TP6B060V17-14, 59TP6B080V17-16, 59TP6B080V21-20, 59TP6B100V21-20, 59TP6B120V24-22
58CU0A58CU0A040C17-12, 58CU0A060C17-16, 58CU0A080C21-20, 58CU0A100C21-20
58SU0A58SU0A040E17-12, 58SU0A060E17-16, 58SU0A080E21-20, 58SU0A100E21-20
59CU5A59CU5A060C17-16, 59CU5A080C21-20, 59CU5A100C21-22
59SU5A59SU5A040E17-12, 59SU5A060E17-16, 59SU5A080E21-20, 59SU5A100E21-20, 59SU5A100E21-22

Where this comes from

Checked against the manufacturer's manual on 9 October 2026.

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Other Carrier gas furnace codes

Code Meaning What you can do
14 Ignition lockout after repeated failed lighting attempts Safe checks first, then a pro
33 Limit circuit fault, a limit or rollout switch is open Safe checks first, then a pro
35 Modulating gas valve not communicating Call a pro
14.1 Ignition lockout after repeated failed lighting attempts Safe checks first, then a pro
34.1 Ignition fault, burners did not light in 4 trials Safe checks first, then a pro
34.2 Flame lost before the heating blower started Safe checks first, then a pro
34.3 Flame lost after the heating blower started Safe checks first, then a pro
34.4 Flame lost at reduced inducer pressure or in Self Healing mode Safe checks first, then a pro
34.5 Low heat flame lost before the blower started Safe checks first, then a pro
34.6 Low heat flame lost after the blower started Safe checks first, then a pro
34.7 High heat flame lost before the blower started Safe checks first, then a pro
34.8 High heat flame lost after the blower started Safe checks first, then a pro

See all ignition failure codes on gas furnaces across brands.