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MEDIUM URGENCY

Carrier Code 34 — Ignition Proving Failure

Code 34 (3 short + 4 long flashes)

Ignition proving failure — flame sensor, igniter, or gas supply issue.

Brand: Carrier (Also covers Bryant, Payne)  |  Equipment: Gas Furnace

What This Code Means

Code 34 means the control tried to ignite the burners but failed to detect flame within the trial period. The control will try up to 3 more times before locking out as code 14.

Likely Causes (Ranked)

Most common (~50%)

Dirty flame sensor

What: Buildup on the flame sensor prevents flame detection.

How to check: Pull sensor (one screw); look for black/white oxide coating.

Fix: Clean with fine emery cloth or steel wool.

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Common

Failed hot surface igniter

What: Igniter cracked, broken, or burned out — won't reach ignition temp.

How to check: Watch igniter during heat cycle — should glow bright orange.

Fix: Replace igniter.

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Common

Low gas pressure or closed valve

What: Insufficient gas reaches the burners.

How to check: Verify furnace gas shutoff is fully open; test other gas appliances.

Fix: Open shutoff; call gas utility about pressure if needed.

Less common

Failed gas valve

What: Gas valve coil failure prevents proper gas flow.

How to check: Tech tests valve electrically.

Fix: Replace gas valve.

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Diagnostic Steps

  1. Cut power 60s to clear retry counter
  2. Watch heat cycle: igniter should glow, gas should flow
  3. If igniter glows but no flame: gas issue
  4. If flame lights but dies: clean flame sensor
  5. If igniter never glows: replace igniter

Frequently Asked Questions

How do I fix Carrier code 34?
Clean the flame sensor first (50% of cases). If that fails, check the igniter.
Does Carrier 34 mean my igniter is bad?
Sometimes — but flame sensor is more common. Try cleaning that first.
How long does a Carrier igniter last?
Typical lifespan is 3-5 years. Hot surface igniters are consumables.

Related Carrier Codes

Carrier Error Code 14Carrier Error Code 22

Related Symptoms

Furnace Not IgnitingFurnace Clicking Not Igniting

Need More Help?

Try our interactive symptom diagnostic tool or browse Carrier parts.

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