🛠️ Tony’s Intro: Don’t Panic, Just Count the Flashes
Let me guess. You opened the panel on your 5-ton Goodman combo system, the board’s blinking like it’s throwing a rave, and the homeowner’s standing over your shoulder saying, “What’s that mean?”
Hey, I’ve been there. It happens to all of us—even the seasoned techs. But here’s the deal: those error codes aren’t just gibberish. They’re the system trying to talk to you. You just gotta know how to listen.
These 5-ton R-32 AC and gas furnace combos have some powerful brains in 'em. The control boards monitor everything from flame sensors to pressure switches, blower speeds, and more. If something goes sideways—even a little bit—it’s gonna throw a code.
So today, I’m walking you through the most common diagnostic codes, what they mean, and how to fix them. Whether you're working on a no-heat call, a cooling failure, or just want to avoid callbacks, this guide’s for you.
Grab your meter, a flashlight, and a fresh filter, and let’s decode that board like pros. 🧢
💡 Where to Find the Error Codes
Before we get into the specifics, you gotta know where the codes live.
Most Goodman furnaces like the GR9T961205DN have an LED on the control board inside the blower compartment. When there’s a fault, it’ll flash a pattern—short, long, repeating, etc. You match that pattern to the error code legend on the inside of the panel door.
Same goes for the outdoor condenser. The GLXS4BA6010 will have a diagnostic light or onboard display. Flash codes vary by model, so always keep the installation manual close. You can grab those straight from Goodman if you don’t have the printed version handy.
🔁 Flash Code Basics: Furnace Edition
Here’s a cheat sheet for some of the most common furnace LED codes and what they mean.
1 flash = Ignition failure
Usually caused by a dirty flame sensor, poor ground, or a gas valve not opening. Pull the flame sensor, clean it with emery cloth, and check your 24V signal to the valve.
2 flashes = Pressure switch stuck closed
Means the switch didn’t reset. Check for water in the tubing, blocked exhaust, or a cracked switch.
3 flashes = Pressure switch stuck open
Could be a blocked intake or inducer issue. Check venting and the inducer motor amperage.
4 flashes = Open limit switch
Your heat exchanger’s too hot. Usually caused by a dirty filter, bad blower motor, or undersized ductwork.
5 flashes = Rollout switch tripped
Serious stuff—this means flames rolled out of the heat exchanger. Don’t just reset it. Find the root cause.
The Building Performance Institute has a solid guide on combustion safety testing if you want to dive deeper into how these safeties work.
🌡️ Cooling System Error Codes: What the Condenser’s Telling You
With R-32 systems like the GLXS4BA6010, you're also dealing with the condenser side of the combo. Most of these units will flash fault codes related to:
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Thermistor (temperature sensor) failure
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High pressure cutout
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Low pressure or no refrigerant
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Control board communication loss
If your outdoor unit won’t kick on and you’ve verified power and contactor coil voltage, check the diagnostic LED (usually behind the access panel). You’ll want to trace the flash pattern and cross-check with the manufacturer’s guide.
And don’t forget: R-32 is mildly flammable (A2L), so always use proper tools and refrigerant-rated leak detectors. You can brush up on A2L handling with the EPA’s refrigerant safety overview.
🔌 Common Root Causes Behind the Codes
Let’s break down what’s really going on when these codes show up.
Pressure switch issues
Usually linked to clogged venting, water in the tubing, or a fan that’s not pulling enough negative pressure. Always verify the switch’s trip range and use a manometer if needed.
Flame sensor failure
If it won’t sense flame after ignition, you’ll get a hard lockout. Clean the sensor, check the ground connection, and ensure the burner’s not obstructed.
High limit trips
Poor airflow is the main culprit. Check static pressure, filter condition, and blower motor settings.
Communication faults
These can pop up if the low-voltage wiring between the thermostat and the board is damaged or miswired. Double-check your C wire and common connections.
🧪 Diagnosing Error Codes Like a Pro
Here’s how I approach a system throwing codes:
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Count the LED flashes and write them down
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Power down and pull the access panel
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Check for obvious issues—dirty flame sensor, clogged drain, burnt wires
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Use a multimeter to test voltages at pressure switches, gas valve, and transformer
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Restart and monitor the sequence of operation
Goodman boards are usually pretty talkative. Once you learn to read their signals, you’ll cut your diagnosis time in half.
🔄 Resetting and Clearing Faults Safely
Now that you’ve found the issue and fixed it, you’ll want to reset the board.
Here’s the proper reset method:
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Turn off power at the furnace switch or breaker
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Wait at least 30 seconds
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Restore power and watch for a solid LED
If it flashes again immediately? You didn’t fix the root problem. Backtrack your steps.
Don’t just power cycle endlessly hoping it’ll go away. These systems are smarter than that.
🔐 Lockouts and How to Clear Them
Some faults—like flame failure or rollout trips—will cause the system to enter a hard lockout. That means it won’t retry again until it’s manually reset.
Lockouts protect the system from repeated ignition attempts or overheating. So before you clear it, make sure you’ve truly fixed the issue.
Goodman furnaces usually reset automatically after a set time unless the issue persists. If not, you’ll have to shut off power and start fresh.
📞 When to Call for Help (Or Back Yourself Up)
Look, we all have those moments. You’ve checked everything, followed the manual, and the system still won’t fire. Don’t be afraid to:
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Call Goodman’s tech support line
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Post on the HVAC School forum for a second opinion
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Reference the AHRI match info to confirm compatibility (ahridirectory.org)
🧠 Wrapping It Up with Tony
Here’s the thing—error codes aren’t there to make your life miserable. They’re built-in diagnostics designed to save your butt when something’s off. Whether it’s a bad sensor, a blocked vent, or a miswired thermostat, the board is trying to help you figure it out.
So don’t just clear the code and run. Learn what it’s telling you. Run your sequence of operations. Measure twice, guess never. That’s how you keep your installs solid and your service calls short.
If you’re setting up one of those 5-ton Goodman R-32 combos and want something with clean documentation and solid diagnostics, I always point folks to The Furnace Outlet’s matched systems. They’ve got the manuals, wiring diagrams, and support you need to set the board up right from the start—so you can spend less time troubleshooting and more time getting paid.
Want to learn how to efficiently charge your R-32 5-ton combo? Visit my guide: One Pound at a Time.
That’s it for now. Keep those leads tight, your voltmeter handy, and your eyes on the board. Catch you next time I’m elbow-deep in a locked-out furnace.
—Tony the Trusted Tech🧢
