Troubleshooting Guide: Common Problems With Goodman 96% Furnaces
If your Goodman 96% AFUE furnace isn’t firing, isn’t staying on, or is giving you cryptic blinking lights at 2 a.m., you don’t need fluff—you need Practical Jake walking you step-by-step through the real fixes.
This is a 3,000-word, no-nonsense troubleshooting guide built for homeowners who want to:
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Try safe, basic fixes
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Understand Goodman error codes
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Clean flame sensors correctly
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Diagnose airflow, venting, and drain issues
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Know exactly when it’s time to stop DIY’ing and call a tech
This guide applies to Goodman 96% AFUE models such as:
GM9C96, GMVC96, GCVC96, GMSS96, GMES96, GR96, GRVT96, and similar high-efficiency two-stage designs.
We’re going deep—real explanations, real steps, real fixes.
1. How Goodman 96% Furnaces Work (So You Know What’s Breaking)
Before troubleshooting, understand what makes a 96% condensing furnace different:
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It condenses moisture inside the secondary heat exchanger
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It produces water that must drain properly
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It uses pressure switches to verify airflow
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It relies on PVC venting rather than metal
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It uses ECM or multispeed blowers
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It has integrated boards with LED error codes
Because these units extract more heat from exhaust gases, they have more safety checks—and those checks are often the source of shutdowns.
2. Quick Fixes You Can Try Immediately (Safe For Homeowners)
These are safe actions ANY homeowner can do without opening sealed combustion chambers or touching gas components.
Quick Fix #1 – Power Cycle the Furnace
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Turn OFF the furnace switch (looks like a light switch).
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Turn OFF the breaker.
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Wait 60 seconds.
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Turn everything back on.
Goodman boards often reset after a hard power cycle.
Quick Fix #2 – Replace or Remove a Clogged Filter
A dirty filter is the #1 cause of:
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Overheating
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Limit switch trips
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Poor airflow
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Pressure switch errors
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Short cycling
If the filter looks gray, fuzzy, bent, or sucked into the rails, it’s starving for airflow.
Use Goodman's recommended filter size (varies by cabinet width).
Great filter reference:
MERV_Filter_Guide
Quick Fix #3 – Check the Thermostat
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Make sure it’s set to HEAT.
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Make sure the setpoint is above room temp.
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Replace batteries.
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Confirm wires aren’t loose at the thermostat terminals.
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For smart thermostats, reboot the device.
Quick Fix #4 – Clear Blocked Intake/Exhaust Pipes (PVC)
Snow, leaves, bugs, lint, or debris in the vent pipes will shut down any 96% furnace.
Outside PVC pipes must be:
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Free of ice
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Free of nests
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Free of blockage
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Not shoved into shrubs or fencing
A clogged vent = pressure switch won’t prove = no flame.
Helpful venting basics:
Furnace_Venting_Rules
Quick Fix #5 – Check the Drain Line for Blockage
96% furnaces make ½–1 gallon of condensate per hour.
If the drain:
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Clogs
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Sags
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Has double traps
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Freezes
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Backs up
…the pressure switches trip, and the furnace locks out.
Clean the trap if possible. Make sure the tubing slopes downward.
Condensate maintenance guide:
Condensate_Trap_Cleaning
Quick Fix #6 – Make Sure the Furnace Door Is On Tight
Goodman furnaces have a safety switch that kills power when the blower door is removed.
If the door isn’t fully seated, the furnace won’t run.
3. Goodman 96% Error Code Explanations (LED Flash Meanings)
Every Goodman 96% furnace uses LED flash codes to explain what’s wrong.
Let’s translate them into normal English.
(Your specific model’s manual has the exact code list, but these are the common ones.)
Steady On Light
Board has power and is waiting for a call.
1 Flash – Ignition Failure
Meaning: Furnace tried to light but couldn’t prove flame.
Likely causes:
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Dirty flame sensor
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Weak ignitor
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Low gas pressure
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Burner not grounding
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Misaligned flame
Try: Clean flame sensor (steps later).
2 Flashes – Pressure Switch Stuck Closed
Meaning: Pressure switch is reading “closed” when it should be open.
Causes:
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Blocked vent
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Blocked intake
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Pressure switch hose full of water
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Condensate backup
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Stuck pressure switch
3 Flashes – Pressure Switch Stuck Open
Meaning: Furnace can’t verify the inducer is pulling proper draft.
Causes:
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Clogged intake/exhaust
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Cracked or loose pressure tubing
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Failed inducer motor
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Condensate trap clogged
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Dirty filter causing low airflow
Fix: Check filter, vents, drain, tubing.
4 Flashes – Limit Switch Open
Meaning: Furnace overheated.
Causes:
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Dirty filter
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Blower not running
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Blocked supply vents
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Undersized ductwork
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Bad blower capacitor
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Motor failure
5 Flashes – Flame Sensed With No Call For Heat
Meaning: Gas valve leaking or electrical feedback.
Call a technician immediately.
6 Flashes – Rollout Switch / Flame Rollout
This is a dangerous condition.
Do NOT reset.
Call a technician.
7+ Flashes – Internal Board Faults
Call a technician.
For official reference materials:
Goodman_Furnace_Diagnostics
4. Flame Sensor Issues (95% of “No Heat” Calls)
If your Goodman furnace:
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Starts the inducer
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Ignites
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Runs for 2–5 seconds
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Then shuts off
…that is a dirty flame sensor almost every time.
Let’s fix it.
4.1 What the Flame Sensor Does
It detects flame using electrical microamps.
If it doesn’t sense flame, it shuts down the gas valve.
High-efficiency furnaces are sensitive—slightly dirty sensors throw errors.
4.2 How to Clean a Flame Sensor (DIY-Safe)
Tools:
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1/4" nut driver
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Fine steel wool or emery cloth
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Soft cloth
Steps:
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TURN OFF power.
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Remove the sensor (one screw).
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Gently polish the metal rod until shiny.
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Do NOT sand aggressively.
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Do NOT touch the ceramic insulator.
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Wipe clean.
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Reinstall.
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Power the furnace back on.
Most furnaces fire immediately after cleaning.
Good guide for sensor issues:
Flame_Sensor_Tips
4.3 When the Flame Sensor Isn’t the Problem
If cleaning doesn’t fix it:
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Ignitor may be weak
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Grounding wire loose
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Gas valve weak
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Burner alignment off
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Low gas pressure
These require a pro.
5. Pressure Switch & Airflow Problems (The Most Annoying Category)
The pressure switch proves the furnace can expel combustion gases safely.
This is where 96% units fail often—because they rely heavily on draft accuracy.
5.1 Common Pressure Switch Issues
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Blocked flue or intake
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Condensate backup in the tubing
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Cracked tubing
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Inducer wheel dirty
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Weak inducer motor
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High static pressure due to duct issues
Proper static pressure testing guide:
Static_Pressure_Explained
5.2 Fixing Pressure Switch Problems (DIY-first approach)
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Inspect PVC intake/exhaust
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Clear leaves, snow, screens
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Replace air filter
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Check that drain line has no dips
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Remove water from pressure tubing
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Ensure furnace door is closed tight
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Restart furnace
If it still won’t fire, the switch or inducer may be failing.
6. Drain Problems (Unique to 96% Furnaces)
Because a condensing furnace produces water, the drain system is a critical component.
6.1 Symptoms of Drain Problems
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Gurgling sounds
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Pressure switch errors
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Furnace clicking but not igniting
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Water leaking inside the cabinet
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The furnace runs for 30–90 seconds then shuts off
6.2 Common Drain Errors
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No slope (needs 1/4" per foot)
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Double-traps
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Plugged trap
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Vinyl tubing kinked
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Drain outlet frozen
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Short horizontal runs cause pooling
Remember:
A clogged trap = no heat.
Drain maintenance reference:
Condensate_Trap_Cleaning
7. When to Call a Technician (Jake’s Hard Line)
You CAN fix simple issues safely, but you SHOULD call a pro if you see:
1. Gas-related symptoms
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Smell of gas
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Gas valve errors
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The flame rollout switch tripped
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Flame present when furnace is off
2. Electrical failures
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Blower motor won’t run
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Inducer motor screeching
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Repeated breaker trips
3. High-limit tripping repeatedly
This means your heat exchanger is overheating.
Call a Technician Immediately If:
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You see melted wiring
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The furnace shuts down with a burning smell
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You get rollout code (dangerous)
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The blower runs continuously without heat
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The inducer won’t start
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You’ve cleaned the flame sensor and still get errors
Also call a pro when:
Your furnace is cycling too often or too rarely
That usually requires measuring static pressure, gas pressure, or temp rise—tools homeowners don’t have.
Your furnace is under a 10-year warranty
Goodman requires licensed tech service for warranty claims.
Technician directory:
Find_Qualified_HVAC_Tech
8. Full Troubleshooting Flowchart (Jake Style)
Furnace won’t turn on →
Check thermostat → check power → check filter → check door switch → check vent → check drain → reset furnace
Furnace starts but shuts off in 5 seconds →
Dirty flame sensor → weak ignitor → grounding issue → bad gas valve
Furnace runs but blows cold air →
Blower failure → gas not flowing → condensate stuck → flame not maintained
Furnace short cycles →
Dirty filter → high static → closed vents → improper fan speed → overheating/limit trips
Furnace ignition delayed →
Dirty burners → weak ignitor → low gas pressure → inducer issues
Loud noises →
Inducer bearings → blower wheel debris → duct expansion popping
In the next blog, you will learn about Maintenance Checklist: Get 15–20 Years Out of This Furnace
