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Carrier furnace status code · Sources read 2026-11-01

Carrier Furnace Code 34: Ignition-Proving Failure

If you smell gas or a CO alarm sounds, leave the home and call the gas utility or 911 from outside.

Code 34 is an ignition-proving failure. Carrier's guides say the control will try three more times before locking out with code 14, and list causes from low inlet gas pressure and a shut-off gas valve to oxide on the flame sensor, a defective hot surface igniter and poor ground continuity.

Talk to a contractor about your Carrier furnace code 34

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One call reaches a contractor registered for your ZIP; ask the fee and the arrival window.

HVAC Responder Editorial Team · Reviewed 2026-11-01 · Facts quoted from manufacturer documentation

HVAC Responder is an independent referral service and is not affiliated with or authorized by Carrier.

How code 34 looks on the furnace light

On these Carrier furnaces the status light shows code 34 as 3 short flashes, then 4 long flashes . Carrier’s 58MVP (Series 170 & 180), 58MVB, 58UVB troubleshooting guide (58-06T) explains the pattern:

EACH OF THE FOLLOWING STATUS CODES IS A TWO DIGIT NUMBER WITH THE FIRST DIGIT DETERMINED BY THE NUMBER OF SHORT FLASHES AND THE SECOND DIGIT BY THE NUMBER OF LONG FLASHES.

Codes differ between furnace generations, so match the series on your furnace’s rating plate to the guide below.

What Carrier’s guides say code 34 means, by furnace series

58CVA / 58CVX

Carrier’s 58CVA / 58CVX troubleshooting guide (TG-GFC80-02) lists code 34 as:

34 IGNITION PROVING FAILURE – Control will try three more times before lockout #14 occurs. If flame signal is lost during blower on-delay period, blower will come on for the selected blower off-delay.

Checks listed in the same guide:

  • Listed check: “Low inlet gas pressure.”
  • Listed check: “Control ground continuity.”
  • Listed check: “Gas valve defective or turned off.”
  • Listed check: “Manual valve shut off.”

Discuss your Carrier furnace code 34 with a contractor

Call (877) 565-3062

One call reaches a contractor registered for your ZIP; ask the fee and the arrival window.

  • Listed check: “Oxide buildup on flame sensor (clean with fine steel wool).”
  • Listed check: “Proper flame sense micro amps (.5 micro amps DC min., 4.0 - 6.0 nominal).”
  • Listed check: “Green/Yellow wire MUST be connected to furnace sheet metal.”
  • Listed check: “Inadequate flame carryover or rough ignition.”
  • Listed check: “Flame sensor must not be grounded.”

58MVP (Series 170 & 180), 58MVB, 58UVB

Carrier’s 58MVP (Series 170 & 180), 58MVB, 58UVB troubleshooting guide (58-06T) lists code 34 as:

34 IGNITION PROVING FAILURE – Control will try three more times before lockout #14 occurs. If flame signal is lost during blower on-delay period, blower will come on for the selected blower off-delay.

Checks listed in the same guide:

  • Listed check: “Low inlet gas pressure.”
  • Listed check: “Control ground continuity.”
  • Listed check: “Gas valve defective or turned off.”
  • Listed check: “Defective Hot Surface Igniter.”
  • Listed check: “Manual valve shut off.”
  • Listed check: “Oxide buildup on flame sensor (clean with fine steel wool).”
  • Listed check: “Proper flame sense micro amps (.5 micro amps DC min., 4.0 - 6.0 nominal).”
  • Listed check: “Green/Yellow wire MUST be connected to furnace sheet metal.”
  • Listed check: “Inadequate flame carryover or rough ignition.”
  • Listed check: “Flame sensor must not be grounded.”

59MN7A (Series 100)

Discuss your Carrier furnace code 34 with a contractor

Call (877) 565-3062

One call reaches a contractor registered for your ZIP; ask the fee and the arrival window.

Carrier’s 59MN7A (Series 100) troubleshooting guide (59MN7A-01T) lists code 34 as:

34 IGNITION PROVING FAILURE – Control will try three more times before lockout #14 occurs. If flame signal is lost during blower on-delay period, blower will come on for the selected blower off-delay.

Checks listed in the same guide:

  • Listed check: “Low inlet gas pressure.”
  • Listed check: “Control ground continuity.”
  • Listed check: “Gas valve defective or turned off.”
  • Listed check: “Defective Hot Surface Igniter.”
  • Listed check: “Manual valve shut off.”
  • Listed check: “Oxide buildup on flame sensor (clean with fine steel wool).”
  • Listed check: “Proper flame sense micro amps (.5 micro amps DC min., 4.0 - 6.0 nominal).”
  • Listed check: “Green/Yellow wire MUST be connected to furnace sheet metal.”
  • Listed check: “Inadequate flame carryover or rough ignition.”
  • Listed check: “Flame sensor must not be grounded.”

Discuss your Carrier furnace code 34 with a contractor

Call (877) 565-3062

One call reaches a contractor registered for your ZIP; ask the fee and the arrival window.

Does code 34 reset on its own?

The guides do not describe an automatic reset for this code.

What to do before you call

  • Write the code down before you touch anything. Carrier’s 58MVP (Series 170 & 180), 58MVB, 58UVB troubleshooting guide (58-06T) starts with: “DO NOT REMOVE BLOWER ACCESS PANEL! Record status of AMBER LED.” Turning off power can also clear the code history.
  • If you smell gas, leave first, then call the utility.
  • Everything else on these lists (gas valve, pressure switches, wiring, venting, the control board) is technician work.

Related codes

All Carrier furnace codes

Furnace guides for the wider symptom

Sources

    Discuss your Carrier furnace code 34 with a contractor

    Call (877) 565-3062

    One call reaches a contractor registered for your ZIP; ask the fee and the arrival window.

    Related equipment, symptoms and component guides

    Use each guide with its named equipment and source. A symptom or code alone does not select a replacement part.

    What happens when you call about your Carrier furnace code 34

    • Your call routes to an independent local contractor registered for your ZIP code.
    • Ask the fee and the arrival window.
    • The decision to hire stays with you.
    Call (877) 565-3062

    One call reaches a contractor registered for your ZIP; ask the fee and the arrival window.

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