Carrier Furnace Won't Ignite: Causes, Fixes & Costs

Last updated Sep 27, 2026 · By fixme.vip Editorial

Carrier furnace won't ignite: what it means

“Won’t ignite” isn’t a single Carrier fault code — it’s a symptom. Your furnace is calling for heat and running through its startup sequence, but the burners never light. On most Carrier boards you’ll hear the inducer motor spin up and, on hot-surface systems, you may see the igniter glow, but the gas never lights or the flame never proves.

Depending on your control board, this symptom usually ends in a specific stored fault code. The most common are ignition-related lockouts: Code 14 (ignition lockout), Code 34 (ignition proving failure), and Code 13 (limit-circuit lockout). If your furnace tried to ignite four or five times and then quit, it has likely gone into hard lockout and will hold until power is cycled or, on some boards, auto-reset after about three hours.

Because ignition failure can involve gas, this is a pro-level repair. Homeowners can safely do a handful of checks, but anything inside the cabinet — igniters, sensors, gas valves, wiring — is technician work.

Carrier furnace won't ignite: common causes, ranked by probability

1. Dirty flame sensor — The furnace lights but the flame isn’t “proven,” so the board shuts the gas off within seconds and eventually locks out. This is the single most common ignition complaint.
2. Worn or cracked hot-surface igniter — The igniter no longer glows hot enough (or at all) to light the gas. Very common on furnaces 5+ years old.
3. Tripped or faulty pressure switch / blocked flue or intake — If the inducer can’t establish proper draft (blocked vent, clogged condensate, cracked hose), the pressure switch won’t close and ignition never starts.
4. Gas supply problem — Closed gas valve, tripped meter, empty propane tank, or low gas pressure. The igniter glows but there’s nothing to burn.
5. Faulty igniter wiring or gas valve — A failed valve won’t open on demand; damaged wiring interrupts the ignition sequence.
6. Control board fault — Less common, but a failed board can mis-sequence or never energize the igniter.
7. Tripped limit switch — An overheated furnace (often from a dirty filter or blocked airflow) can trip the high-limit, blocking ignition.

Where the sequence ends in a stored code, Carrier’s own troubleshooting order applies — see Code 14 and Code 34 for the manufacturer’s ignition diagnostic flow.

How to fix Carrier furnace won't ignite: safe checks first

These are the only steps you should do yourself:

• Thermostat: Confirm it’s set to HEAT and the target temp is above room temperature. Replace the batteries if it’s battery-powered.
• Air filter: A clogged filter chokes airflow and can trip the limit switch. Swap in a clean filter if yours is dirty.
• Breaker and furnace switch: Check the furnace breaker in your panel and the switch on or near the furnace (it looks like a light switch). Reset a tripped breaker once.
• Gas supply (homeowner-visible only): Confirm the manual gas shutoff valve at the furnace is in the ON position (handle parallel to the pipe) and that other gas appliances (stove, water heater) are working. Do not disassemble or adjust anything. If you smell gas, leave and call your gas utility’s emergency line or 911.
• Vents and registers: Make sure supply and return vents throughout the house are open and unblocked.
• Condensate line: On high-efficiency models, a clogged condensate trap can trip the pressure switch. Check for standing water or a full condensate pan.
• One reset: You may cycle the furnace off and on once at the switch to clear a temporary lockout. If it still won’t ignite, stop and call a pro. Do not reset repeatedly.

How a technician will diagnose it

A qualified tech will:

1. Read the stored fault code by counting the LED flashes or checking the control-board display.
2. Watch a full ignition cycle to see exactly where it fails — inducer, pressure switch, igniter glow, gas valve opening, flame proving.
3. Test the hot-surface igniter for resistance/continuity with a multimeter and inspect it for cracks.
4. Check the flame sensor microamp signal and clean or replace it if the flame isn’t proving.
5. Verify draft and the pressure switch — checking the flue, intake, inducer, and hoses for blockages, then confirming the switch closes.
6. Measure gas pressure at the valve and confirm the valve opens on demand.
7. Inspect wiring, connections, and the control board for faults if all else checks out.

This lets you sanity-check a quote: a reputable tech starts with the flame sensor and igniter (cheap, common) before recommending a board or gas valve (expensive, rare).

Symptom, cause and what to do

Carrier furnace won't ignite repair cost

Honest US ranges, parts and labor combined (diagnostic fee often $80–$150, sometimes waived if you proceed):

• Flame sensor cleaning/replacement: $80–$250
• Hot-surface igniter replacement: $150–$350
• Pressure switch replacement: $150–$350
• Flue/intake or condensate clearing: $100–$300
• Gas valve replacement: $300–$600
• Control board replacement: $400–$700
• Filter or thermostat batteries (DIY): $0–$40

Because “won’t ignite” can be a $0 filter fix or a $600 gas-valve job, insist on a diagnosis of the actual failure point before authorizing major parts.

Related codes

• Carrier Furnace Code 14: Ignition Lockout Causes & Fixes — the hard-lockout this symptom often ends in.
• Carrier Furnace Code 34: Ignition Proving Failure & Fixes — flame not proven after ignition.
• Carrier Furnace Code 13 — limit-circuit lockout.
• Carrier Furnace Flame Sensor Problems: Causes & Fixes — the #1 cause of light-then-shutoff.
• Carrier Furnace Ignition Lockout: Causes, Fixes & Costs — general lockout guidance.
• Carrier Furnace Clicking But Not Starting: Causes & Fixes — related no-start behavior.
• Carrier Furnace Blowing Cold Air: Causes & Fixes — when ignition partially succeeds.
• Carrier Furnace Gas Smell: What to Do & When to Call 911 — read first if you smell gas.