Heil Furnace Code 6: What It Means & How to Fix It
Compiled & reviewed by the HVAC Flash Codes editorial team · Updated 2026-06-25 · confidence: high
⛔ Stop — call a licensed pro
What does Heil furnace code 6 mean?
Ignition proving failure — flame was not proven during the trial for ignition; the control tries again before locking out (code 6+1). Most often caused by Gas supply off or low inlet gas pressure.
What your furnace LED does. The diagnostic light blinks 6 flashes, pause, repeat — that pattern is Heil furnace code 6.
What Heil furnace code 6 means
Ignition proving failure — flame was not proven during the trial for ignition; the control tries again before locking out (code 6+1).
Common causes
Gas supply off or low inlet gas pressure
Defective hot-surface igniter
Dirty flame sensor (oxide buildup)
Control grounding problem
Homeowner-safe steps to try
Confirm other gas appliances in the home work (rules out a household gas-supply issue)
Set the thermostat OFF, power-cycle the furnace at the breaker for a minute, then restore to allow another ignition trial
Replace a dirty filter and confirm vents are open
When to call a licensed HVAC technician
If the basic checks below don't clear the code, the fault recurs, or anything involves the gas valve, burners, flame sensor or wiring, stop and book a licensed HVAC technician. Repairs to the combustion or gas system are not DIY.
⚠️ Safety first. Gas furnaces burn fuel and produce combustion gases. If you ever smell gas (a rotten-egg or sulfur odor), hear hissing, or your carbon-monoxide alarm sounds, do not touch light switches, thermostats, or the furnace — leave the home immediately and call your gas utility's emergency line or 911 from outside. Homeowners should limit themselves to simple, safe steps: setting the thermostat, checking and replacing the air filter, confirming the furnace switch and breaker are on, keeping supply registers and return grilles open, and clearing snow, ice, or debris from outdoor vent and intake terminations. Never bypass, jumper, or reset safety switches (limit, flame-rollout, or pressure switches), never open the gas valve or burner compartment, and never attempt combustion, electrical, or control-board repairs yourself. Error codes point toward a problem but are not a substitute for proper diagnosis — when in doubt, turn the system off and call a licensed HVAC technician. Keep working carbon-monoxide detectors on every level of your home.
When to call a pro: Call a licensed HVAC technician if the furnace still fails to ignite — the igniter, flame sensor, and gas valve aren't homeowner-serviceable. If you smell gas, do NOT touch switches; leave and call your gas utility or 911 from outside.
Heil furnace code 6 FAQ
What does Heil furnace code 6 mean?
Ignition proving failure — flame was not proven during the trial for ignition; the control tries again before locking out (code 6+1).
What causes Heil furnace code 6?
Common causes: Gas supply off or low inlet gas pressure; Defective hot-surface igniter; Dirty flame sensor (oxide buildup); Control grounding problem.
Can I fix Heil furnace code 6 myself?
You can safely try: Confirm other gas appliances in the home work (rules out a household gas-supply issue); Set the thermostat OFF, power-cycle the furnace at the breaker for a minute, then restore to allow another ignition trial; Replace a dirty filter and confirm vents are open. Call a licensed HVAC technician if the furnace still fails to ignite — the igniter, flame sensor, and gas valve aren't homeowner-serviceable. If you smell gas, do NOT touch switches; leave and call your gas utility or 911 from outside.
Sources: shareddocs.com. General information for homeowners, not professional advice — confirm against your furnace's manual and a licensed technician.