When your furnace won’t start, your brain usually jumps straight to “How much is this going to cost me?”
Savvy pause. Breathe. Most furnace no-start issues fall into a small, predictable set of causes—and many of them can be identified safely before you ever call a pro.
This guide walks you through a logical, homeowner-safe diagnostic flow for Goodman gas furnaces, especially high-efficiency 96% AFUE models. Think of it as first aid, not surgery.
80,000 BTU 96% AFUE Upflow/Horizontal Single Stage Goodman Gas Furnace - GR9S960803BN
🚨 First Things First: Safety Before Troubleshooting
Before touching anything:
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If you smell gas: Stop immediately, leave the house, and contact your gas utility.
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If a carbon monoxide alarm is sounding: Get outside and call emergency services.
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If the furnace repeatedly tries to start and fails: Do not keep resetting it.
Savvy Rule #1: No heat is uncomfortable. Unsafe heat is dangerous.
🔌 Step 1: Confirm the Furnace Has Power (Yes, Really)
You’d be surprised how often this is the issue.
Check These 5 Power Points:
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Furnace switch (looks like a light switch near the unit)
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Circuit breaker (gas furnaces still need electricity)
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Furnace door panel (must be fully seated)
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GFCI outlet nearby (especially in basements)
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Recent power outage or surge
Savvy insight:
Goodman furnaces have safety switches that intentionally shut everything down if power or panel alignment is off—even slightly.
🔗 External reference:
👉 https://www.energy.gov/energysaver/home-heating-systems
🌡️ Step 2: Thermostat Problems That Masquerade as Furnace Failure
Before blaming the furnace, interrogate the thermostat.
Quick Thermostat Checklist:
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Set to HEAT, not AUTO or OFF
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Temperature set 5+ degrees above room temp
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Fresh batteries (even “smart” stats can fail)
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Correct system type (gas furnace, not heat pump)
Common homeowner mistake:
Replacing a thermostat without configuring it correctly for a gas furnace. That alone can stop ignition entirely.
🔗 External reference:
👉 https://www.consumerreports.org/appliances/thermostats/how-to-program-a-thermostat-a6968368252/
🔥 Step 3: Is Gas Actually Reaching the Furnace?
No gas = no ignition. Simple, but often overlooked.
What to Check Safely:
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Gas shutoff valve near the furnace (handle should be parallel to pipe)
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Other gas appliances (stove, water heater) working?
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Recent gas work or utility interruption?
Savvy warning:
Do not attempt to adjust internal gas valves. Homeowner checks stop at the external shutoff.
🔍 Step 4: Read the Furnace’s Built-In Clues (LED Error Codes)
Goodman furnaces are talkative—if you know how to listen.
How to Read Goodman Error Codes:
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Remove the lower access panel
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Look for a blinking LED on the control board
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Count the flashes (short + long)
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Match the code to the diagnostic chart
Common meanings include:
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Pressure switch issues
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Ignition failure
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Flame sensor problems
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Limit switch trips
Savvy insight:
The furnace locks out on purpose to protect itself. Repeated resets without fixing the cause can make things worse.
🌬️ Step 5: Airflow Issues That Prevent Startup
High-efficiency furnaces are extremely sensitive to airflow.
Check These Airflow Killers:
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Dirty air filter (top cause)
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Closed or blocked vents
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Collapsed return duct
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Recently added thick “allergy” filter
Why this matters:
Restricted airflow causes overheating, which triggers safety shutdowns before ignition or mid-cycle.
🔗 External reference:
👉 https://www.epa.gov/indoor-air-quality-iaq
🔥 Step 6: Ignition Problems — When the Furnace Tries (But Fails)
If you hear clicking or see brief flame before shutdown, ignition is likely the issue.
Common Culprits:
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Dirty flame sensor
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Failing hot surface igniter
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Moisture in the combustion system
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Weak ground connection
Homeowner-safe fix:
Cleaning the flame sensor only if accessible using a soft cloth—no sandpaper, no scraping.
Not homeowner-safe:
Replacing igniters, modifying wiring, bypassing sensors.
🔗 External reference:
👉 https://www.thisoldhouse.com/heating-cooling/why-is-furnace-maintenance-important
💨 Step 7: Venting & Condensate Problems (High-Efficiency Specific)
96% AFUE furnaces produce condensation—and that introduces new failure points.
What Can Stop Startup:
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Frozen or clogged PVC exhaust/intake pipes
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Full or blocked condensate trap
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Kinked drain hose
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Improper slope in venting
Savvy winter tip:
After deep freezes, always inspect exterior vent pipes for ice or snow blockage.
🔗 External reference:
https://www.rbastl.com/wp-content/uploads/sites/2/2019/08/Condensation-Brochure-for-Web.pdf
🔄 Step 8: Resetting the Furnace (Once, and Only Once)
A reset can help—but only once.
Proper Reset Method:
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Turn thermostat OFF
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Shut furnace power OFF for 60 seconds
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Restore power
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Set thermostat to HEAT
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Observe one full startup attempt
If it fails again:
Stop. Continuous resets can damage the control board or igniter.
📞 Step 9: Knowing When It’s Time to Call a Pro
Call an HVAC technician if:
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Error codes repeat after airflow and power checks
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The furnace ignites then shuts down repeatedly
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You smell burning plastic or electrical odor
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The unit is under warranty (DIY may void coverage)
🧠 Savvy Final Takeaway: Don’t Panic—Diagnose Smart
Most Goodman furnace no-start issues are:
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Power related
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Thermostat related
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Airflow related
And many can be identified safely in under 15 minutes.
Your job as a homeowner isn’t to fix everything—it’s to gather clean, accurate information so the fix is faster, safer, and cheaper.
