Completely dead
No blower, no inducer sound, no thermostat response, or the furnace cabinet light is off.
Start here: Start with house power, the furnace service switch, breaker, and the blower door panel seating on its switch.
Furnace ignition problem
Furnace Won’t Ignite After Storm
Direct answer: After a storm, a furnace that will not ignite is usually dealing with a simple interruption first: tripped power, thermostat reset, a loose blower door, or a safety lockout after failed starts. If the inducer starts but the burners never light, the next most common causes are a dirty furnace flame sensor, a failed furnace igniter, or a venting problem from wind or water.
Most likely: Start with power, thermostat mode, filter and door fit, then watch one startup attempt. That one observation usually separates a basic reset issue from an ignition or venting fault.
Storms knock out more than utility power. A quick outage, voltage dip, wind down the vent, or water around the intake can leave a furnace sitting in lockout even after the house power is back. Reality check: a lot of post-storm no-heat calls end up being a reset, door switch, or thermostat issue. Common wrong move: flipping the furnace switch on and off over and over without watching what the unit actually does.
Don’t start with: Do not start by replacing deep furnace parts, opening gas piping, or bypassing safety switches.
If the furnace is completely deadCheck the service switch, breaker, blower door fit, and thermostat batteries or display first.
If the furnace tries to start but never lightsListen for the inducer motor, then look for a glowing igniter and any blinking fault light through the sight glass.
Last reviewed: 2026-04-05
What the furnace does right after the storm matters
Tries to start but no flame
You hear a small motor or clicking, but the burners never light.
Start here: Watch one startup cycle and check whether the igniter glows. That separates igniter trouble from airflow or vent safety issues.
Lights briefly then shuts off
Burners come on for a few seconds and then drop out.
Start here: A dirty furnace flame sensor is high on the list, especially if the furnace was working before the storm.
Runs blower only or short cycles
The blower runs with no heat, or the furnace keeps trying and stopping.
Start here: Check thermostat settings, filter restriction, and any fault light pattern before trying repeated resets.
Most likely causes
1. Power interruption or loose access panel after the outage
Storm outages and quick resets commonly leave a tripped breaker, switched-off service disconnect, or blower door not fully seated on the safety switch.
Quick check: Confirm the thermostat is calling for heat, the furnace switch is on, the breaker is fully reset, and the blower door is tight and flush.
2. Safety lockout after failed ignition attempts
A furnace that tried to light during unstable power or rough vent conditions may stop trying until power is cycled once at the furnace switch.
Quick check: Turn the furnace off for about a minute, restore power, and watch exactly one heat call from start to finish.
3. Dirty furnace flame sensor or failed furnace igniter
If the inducer runs and the sequence gets to ignition but the burners do not stay lit, these are the most common serviceable furnace-side parts.
Quick check: Look through the burner sight area. No glow points toward the furnace igniter. Brief flame that drops out points toward the furnace flame sensor.
4. Storm-related venting or pressure problem
High wind, debris, snow, or water at the intake or exhaust can keep the pressure proving sequence from completing, so ignition never starts.
Quick check: Inspect the outside vent terminations for blockage, sagging screens, standing water, or obvious debris without taking venting apart.
Step-by-step fix
Step 1: Make sure the furnace actually has a clean call for heat
Post-storm furnace problems often look serious when the real issue is lost power, a thermostat reset, or a cabinet panel not engaging the door switch.
- Set the thermostat to Heat and raise the set temperature at least 3 to 5 degrees above room temperature.
- If the thermostat screen is blank or acting odd after the outage, replace batteries if your model uses them or restore its power source.
- Check the furnace service switch near the unit and make sure it is on.
- At the electrical panel, reset the furnace breaker by turning it fully off, then fully back on once.
- Remove and reinstall the blower door or burner access panel so it sits square and fully presses the furnace door switch.
Next move: If the furnace starts normally now, the storm likely caused a simple power or panel-switch interruption. If the furnace is still dead or only partly wakes up, move on and watch the startup sequence.
What to conclude: You have ruled out the easiest no-heat causes before getting into ignition parts or venting.
Stop if:
- The breaker trips again right away.
- You smell gas anywhere around the furnace.
- You see water inside the burner area or electrical compartment.
Step 2: Reset one time, then watch one full startup attempt
A single controlled reset can clear a temporary lockout. Watching one cycle tells you far more than repeated random resets.
- Turn the furnace off at the service switch for about 60 seconds, then turn it back on.
- Stand where you can hear the furnace and see the burner sight glass or inspection window.
- Call for heat at the thermostat and watch the order of events: inducer motor, igniter glow, burner flame, then blower.
- Note whether you hear only a hum, a click, a rush of air, brief flame, or nothing after the inducer starts.
- If there is a visible fault light, note the blink pattern for your manual or service label, but do not start replacing parts from the code alone.
Next move: If the furnace lights and stays on after one reset, keep an eye on it through the next few cycles because the storm may have caused a temporary lockout only. If it fails again, use what you saw to narrow the problem instead of resetting it repeatedly.
What to conclude: No igniter glow points one way, brief flame points another, and no pressure-proving sequence points toward venting or safety shutdown.
Stop if:
- The furnace bangs, pops, or flashes back at the burners.
- You smell gas after a failed start attempt.
- The unit tries repeatedly without lighting and you are tempted to keep cycling power.
Step 3: Check the simple airflow and vent conditions storms commonly disturb
A clogged filter or blocked vent can stop the ignition sequence or cause the furnace to shut down quickly, and both are common after heavy wind and debris.
- Pull the furnace filter and check whether it is packed with dust, damp, or collapsed. Replace it only if it is clearly dirty or wet.
- Look around the furnace base and vent connections for signs of water entry, rust streaks, or dripping condensation.
- Go outside and inspect the furnace intake and exhaust terminations if they are safely reachable from the ground.
- Clear away leaves, lint, nests, snow, or windblown debris at the vent openings without disassembling the vent system.
- If the vent area is wet or partially flooded, leave the furnace off and let a pro inspect it before restart.
Next move: If a blocked vent opening or bad filter was the issue, the furnace may return to normal startup on the next call for heat. If vent openings are clear and the filter is good, focus on the ignition sequence inside the furnace.
Stop if:
- You find standing water in or around the furnace cabinet.
- A vent pipe is loose, disconnected, crushed, or badly corroded.
- You would need a ladder, roof access, or vent disassembly to keep checking.
Step 4: Separate flame-sensor behavior from igniter behavior
These two faults look similar to homeowners, but the startup clues are different and they lead to different repair choices.
- Watch for the hot surface igniter through the sight glass. It should glow before gas lights on many furnaces.
- If you never see igniter glow and the furnace reaches that point in the sequence, the furnace igniter is a likely failed part.
- If the burners light for a few seconds and then shut off, the furnace flame sensor is a likely culprit.
- If you are comfortable opening the burner compartment with power off, inspect the flame sensor rod for heavy white or gray buildup and the igniter for visible cracks.
- Clean only the furnace flame sensor with a gentle dry abrasive pad or very fine abrasive cloth, then reinstall it carefully. Do not touch the igniter element or scrub it.
Next move: If the burners now stay lit, the flame sensor was likely fouled and the repair may be complete. If there is still no igniter glow, or the igniter is cracked, replacement is the likely next step. If the flame still drops out after sensor cleaning, stop and schedule service.
Stop if:
- You are not comfortable removing the burner access panel.
- The igniter is fragile and you would have to force wiring or brackets.
- Any gas smell appears while the compartment is open.
Step 5: Finish with the right next action instead of guessing
By this point you should know whether this is a simple reset issue, a likely flame-sensor problem, a likely igniter failure, or a venting or safety problem that needs a technician.
- If the furnace now starts and runs through a full heating cycle, reinstall all panels securely and monitor the next two or three calls for heat.
- If the burners light briefly then shut off again after flame-sensor cleaning, schedule service rather than guessing at deeper controls.
- If the igniter never glows and you confirmed power, thermostat call, panel fit, filter condition, and clear vents, a matching furnace igniter is the most supported replacement branch.
- If the furnace stays completely dead after power checks, or if the blower runs but the ignition sequence never begins, the problem may be a door switch, control issue, or another fault that needs deeper diagnosis.
- If there is any gas odor, repeated breaker tripping, water intrusion, or damaged venting, leave the furnace off and call for service now.
A good result: If the furnace heats normally and repeats the cycle without fault, you likely cleared the storm-related interruption or corrected a minor ignition issue.
If not: If it still will not ignite, stop at the evidence you gathered and use that to book service or buy only the clearly supported part.
What to conclude: The goal is a clean decision: monitor, replace the likely confirmed part, or escalate before a safe furnace problem turns into a bigger one.
Stop if:
- You are down to guessing between multiple electrical or combustion parts.
- The furnace cabinet has water damage or soot marks.
- Any safety device appears to be bypassed, loose, or tampered with.
Replacement Parts
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FAQ
Can a storm really keep a furnace from igniting?
Yes. A storm can cause a brief power interruption, thermostat reset, vent blockage, moisture around the unit, or a safety lockout after failed starts. Those are all common reasons a furnace will not ignite right after bad weather.
Should I keep resetting the furnace until it lights?
No. One reset is reasonable after an outage. Repeated resets can flood the unit with failed start attempts, hide the real clue, and make a gas or ignition problem less safe.
How do I know if it is the furnace flame sensor or the furnace igniter?
If the burners light and then shut off within a few seconds, suspect the furnace flame sensor. If the furnace reaches the ignition part of the sequence but you never see the igniter glow, suspect the furnace igniter.
What if the blower runs but there is no heat after the storm?
That can happen when the thermostat is mis-set, the furnace is in lockout, or the burners never ignite. Start with thermostat mode, filter condition, and a single observed startup cycle before assuming the blower is the problem.
When should I call a pro instead of trying one more check?
Call right away if you smell gas, see water inside the furnace, have repeated breaker trips, find damaged venting, or still cannot separate a simple reset issue from a combustion or control problem. Those are not good guess-and-buy situations.