Modern furnaces don't just break — they tell you why they broke. The status light on your furnace blinks error codes that diagnose problems before you call a tech. Here's how to read them.
Where to Find the Status Light
Look through the small sight glass or window on the furnace access panel. You'll see a small LED light blinking. Some furnaces also display codes on a digital screen. If you can't see through the panel, the code is usually also on a sticker inside the access door.
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How to Read Blink Codes
Most furnaces use a blink pattern: the light flashes a certain number of times, pauses, then repeats. Count the flashes before the pause — that's your code. For example: 3 flashes + pause + 3 flashes = Code 33.
Common Goodman/Amana Error Codes
| Code | Meaning | What to Do |
|---|---|---|
| 1 flash | System lockout — ignition failure | Check gas supply, try reset button once |
| 2 flashes | Pressure switch stuck open | Check condensate drain, check inducer motor |
| 3 flashes | Pressure switch stuck closed | Inducer motor issue, call tech |
| 4 flashes | Open high limit device | Check filter, check airflow — likely overheating |
| 5 flashes | Flame sensed without call for heat | Gas valve issue, call tech |
| 6 flashes | 115V AC power reversed | Check wiring polarity, call electrician |
| Continuous | Normal operation | Nothing — furnace is running fine |
Common Carrier Error Codes
| Code | Meaning | What to Do |
|---|---|---|
| 13 | Limit device lockout | Check filter and airflow |
| 14 | Ignition lockout | Check gas, try reset |
| 21 | Gas heating lockout | Call tech |
| 33 | Limit/rollout switch open | Check filter immediately — overheating risk |
| 45 | Control board failure | Replace control board or call tech |
The #1 Error Code Cause
Code 4 (high limit) on Goodman and Code 33 on Carrier are both caused by the same thing 80% of the time: a dirty air filter restricting airflow and causing the heat exchanger to overheat. Check your filter before calling anyone.
If your furnace keeps erroring out and it's over 15 years old, it may be time to replace. See factory-direct options at Furnace Direct.
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