Carrier Error Code 34: Ignition proving failure (Furnace)

Updated October 13, 2026 · by Aurora Star Tech Inc.

Carrier error code 34 on a furnace means: Ignition proving failure. It is also called Carrier diagnostic code 34.

High severityFurnace59TP6A · 58SB0A/58SB1A

Homeowner? What Carrier code 34 means for you

Call a technician Your furnace is reporting: Ignition proving failure. The furnace has locked out or cannot run properly. One reset is fine; if the code comes back, it needs a licensed technician to find the cause.

Safe things you can check yourself

Check the thermostat: right mode (Heat or Cool), set a few degrees past room temperature, and fresh batteries if it uses them.
Make sure the unit has power: its on/off switch (often looks like a light switch near the unit) is ON and the breaker in the electrical panel is not tripped.
Make sure the furnace front door or panel is closed properly; many furnaces will not run with the door switch open.
Look at the air filter. If it is grey and clogged, replace it; a blocked filter causes many shutdowns.
Outside, make sure the intake and exhaust pipes or vent cap are not blocked by snow, ice, leaves or a nest.
Check that the gas valve next to the furnace is open (handle in line with the pipe). Do not force it.
Try one reset: turn the power off for 30 seconds, then back on. If the code comes back, stop resetting and call a technician.

Call (647) 657-2977 Book a service call

Licensed technicians serving Vaughan, Toronto and the GTA.

What does Carrier error code 34 mean?

Flame was not sensed during trial for ignition; the control retries 3 more times before lockout 14. If flame is lost during blower on-delay, the blower runs its off-delay.

Applies to: 59TP6A two-stage variable-speed ECM multipoise condensing gas furnace, all sizes (040-10 to 120-22)

Common causes of Carrier code 34

Gas valve or manual shutoff off
Green/yellow ground wire not connected to sheet metal
Flame sensor grounded, dirty or mislocated

A technician checks these and 4 other possible causes on site before replacing any part.

Safety: Gas, electrical and refrigerant work must be done by a licensed technician. Turn off power and gas before servicing, never bypass a safety control, and always follow the manufacturer's manual for your exact model.

Carrier models that use code 34

Show all 22 models

58SB0A045E14--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 59TP6A040-10 59TP6A040-12 59TP6A060-12 59TP6A060-14 59TP6A080-16 59TP6A080-20 59TP6A100-20 59TP6A120-22

Other Carrier Furnace codes

Code	Meaning
31.2	Secondary pressure switch (HPS) open
31.3	Secondary pressure switch lockout
32	Low-heat pressure switch did not close or reopened
32.1	Main pressure switch (LPS) open
33	Limit circuit fault
33.1	Main limit circuit switch open
34.1	Ignition fault during ignition trials
34.2	Flame lost before blower on-delay
34.3	Flame lost after blower on-delay
43	Low-heat pressure switch open while high-heat switch closed
45	Control circuitry lockout
45.1	Control failure - flame circuit / memory / sequence

All Carrier Furnace error codes →

Carrier code 34: homeowner questions

What does Carrier code 34 mean?

Ignition proving failure. Flame was not sensed during trial for ignition; the control retries 3 more times before lockout 14. If flame is lost during blower on-delay, the blower runs its off-delay.

Is it safe to keep using my furnace with code 34?

It depends on the cause. The furnace has locked out or cannot run properly. One reset is fine; if the code comes back, it needs a licensed technician to find the cause.

Can I reset Carrier code 34 myself?

You can try one reset (power off for 30 seconds, then on). If Carrier code 34 comes back, the cause is still there and a licensed technician should check it.

Who can fix Carrier code 34 near me?

Aurora Star Tech Inc. repairs Carrier furnaces in Vaughan, Toronto and across the GTA. Call (647) 657-2977 or book a service call online.

Homeowner help: Furnace Not Turning On: What to Check · Furnace Blinking Light: What the Flash Codes Mean

Troubleshooting guides

Blowing cold air All brands · Furnace
No heat All brands · Furnace
Short cycling All brands · Furnace
Burners will not light or stay lit - Carrier 58SB0A/58SB1A Carrier · Furnace
Furnace not responding to thermostat - Carrier 58SB0A/58SB1A Carrier · Furnace

Source: Carrier 59TP6A Installation, Start-up, Operating and Service Instructions, Fig. 66 Troubleshooting Guide (cont.), p.89; Component Self-Test p.77. Written in our own words as a summary; always check the original manual.

General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.