Decode Those Flashing Lights: What Your Goodman Furnace Error Codes Re

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If your Goodman furnace isn’t heating and you’re staring at a little LED light blinking back at you, here’s the good news:

👉 Your furnace is not broken beyond hope.
👉 It’s telling you exactly what’s wrong.

The bad news? Most homeowners don’t know how to listen.

I’ve lost count of how many service calls start with, “It’s just blinking… I don’t know what that means.” That blinking light is the difference between a five-minute fix and a five-hundred-dollar mistake.

100,000 BTU 96% AFUE Upflow/Horizontal Two Stage Goodman Gas Furnace - GR9T961004CN

Let’s decode it — step by step.

🔍 First: Why Goodman Furnaces Use Flashing Error Codes

Modern Goodman furnaces (especially 96% AFUE models) are designed to shut down safely when something isn’t right. Instead of guessing, the control board flashes a code that points to the problem area.

Think of it like this:

The furnace won’t guess
It won’t push through a safety issue
It will stop and explain itself

You just need to know the language.

📍 Where to Find the Error Code (Don’t Skip This)

Before decoding anything, you need to see it correctly.

What to do:

Turn off room lights if needed
Remove the blower compartment door
Locate the control board LED
Watch the flash pattern carefully

⚠️ Important:
The door switch must be pressed in for the furnace to power up. If the light disappears when you remove the door, that’s normal.

🧠 How Goodman Error Codes Work (Simple Version)

Most Goodman furnaces use flash patterns, not numbers.

Short flash
Pause
Repeat

You count the flashes between pauses.

Example:

Flash-Flash-Pause-Flash-Flash-Pause = 2 flashes

That’s your diagnostic starting point.

📘 Official Goodman diagnostic reference:
https://www.goodmanmfg.com/resources/hvac-learning-center

🔌 🔦 Code: No Light at All (Dead Control Board?)

What it usually means:

No power to the furnace
Door switch not engaged
Blown fuse or tripped breaker

What to check first:

Furnace switch (looks like a light switch nearby)
Breaker panel
Furnace door seated properly

Jake’s take:
If there’s no light, don’t blame the furnace. Blame electricity — until proven otherwise.

🌬️ 🔁 2 Flashes: Pressure Switch Open (Very Common)

This is one of the most frequent cold-weather codes I see.

What it really means:

The furnace tried to start, but airflow or venting didn’t prove safe operation.

Common causes:

Snow or ice blocking PVC vent pipes
Clogged condensate drain
Frozen pressure switch tubing
Improper vent slope from installation

🔗 Venting & pressure switch basics:
https://www.energy.gov/energysaver/furnaces-and-boilers

Jake’s tip:
Always check outside first. A blocked exhaust pipe will shut everything down — instantly.

🔥 🔁 3 Flashes: Pressure Switch Stuck Closed

This one confuses homeowners.

What it means:

The pressure switch is showing “closed” before the furnace even starts.

Likely causes:

Water trapped in pressure tubing
Failed pressure switch
Control board sensing an impossible condition

Jake’s rule:
If the furnace is telling you something happened before it even started, stop and inspect — don’t reset blindly.

🌡️ ⚠️ 4 Flashes: High Limit Switch Open (Overheating)

This code tells you the furnace protected itself from overheating.

Almost always caused by:

Dirty air filter
Blocked supply or return vents
Blower airflow issues

🔗 Airflow and limit switch explanation:
https://hvacoptimizer.net/goodman-furnaces-troubleshooting/

Jake’s warning:
Repeated limit trips don’t “go away.” They crack heat exchangers and shorten furnace life.

🔥 ❌ 6 Flashes: Ignition Failure

This one creates panic — but stay calm.

What it means:

The furnace tried to light the burners and failed to prove flame.

Check these first:

Is the gas valve on?
Are other gas appliances working?
Flame sensor dirty?

A dirty flame sensor is cheap, common, and fixable.

🔗 Ignition & flame sensor overview:
https://www.partshnc.com/blog/goodman-furnace-troubleshooting-guide

Jake’s reality check:
Clean before you replace. Always.

🧯 🚫 7 Flashes: Flame Detected Without Gas Valve Open

This one matters.

What it means:

The control board thinks flame exists when it shouldn’t.

Possible causes:

Faulty flame sensor
Control board failure
Grounding issues

⚠️ This is not a DIY guessing game.

🔗 Goodman service guidance:
https://www.goodmanmfg.com/support/find-a-dealer

🔄 Continuous Flashing: Normal Operation (Yes, Really)

Not all flashing is bad.

Often means:

Furnace operating normally
No stored faults

Jake’s reminder:
Read the manual before assuming blinking = broken.

🛑 What NOT to Do When You See an Error Code

🚫 Don’t keep resetting power
🚫 Don’t bypass safety switches
🚫 Don’t replace parts without diagnosis
🚫 Don’t ignore repeat codes

Every reset without fixing the cause adds wear.

🧰 Jake’s Quick Error Code Checklist

✔ Count flashes correctly
✔ Check vents and drains first
✔ Inspect filter and airflow
✔ Confirm gas supply
✔ Clean flame sensor if needed
✔ Stop if safety codes repeat

Diagnosis beats guesswork — every time.