What each Trane code means — and what to do next. Stuck? AAA Comfort Air fixes Trane systems across Central NJ, often same-day.
Trane and American Standard are known for rugged, long-lasting furnaces and air conditioners. Their control boards flash a red LED diagnostic code.
View the red LED through the sight glass on the blower door and count the flashes; the pattern repeats. The indicator is a red LED flash code.
| Code | What it means | What to do |
|---|---|---|
| LED off | No power | Check breaker & door switch |
| Slow flash | Normal — no call for heat | No action needed |
| Fast flash | Normal — running | No action needed |
| Steady ON | Control board fault | Call us |
| 2 flashes | Lockout on retries (failed ignition) | Flame sensor/igniter/gas — call us |
| 4 flashes | Open limit switch (overheating) | Replace a dirty filter / clear airflow |
| 5 flashes | Flame sensed with gas valve off | Call us |
| 6 flashes | Reversed line-voltage polarity | Wiring — call us |
| 7 flashes | Gas valve circuit fault | Call us |
| 8 flashes | Weak flame-sense signal | Clean/replace the flame sensor — call us |
| 9 flashes | Igniter fault | Call us |
⚠️ Codes can vary by model and control-board revision — always confirm against the label inside your unit’s access panel. For any gas, electrical, or refrigerant fault, call a licensed technician.
View the red LED through the sight glass on the blower door and count the flashes; the pattern repeats.
You can try one power cycle at the breaker to clear a one-time fault. But if the same code returns, it’s a real fault — repeatedly resetting a gas or electrical issue can be unsafe. Call AAA Comfort Air at 609-665-3022.
AAA Comfort Air installs and repairs Trane systems across Cream Ridge and Central New Jersey, with same-day and 24/7 emergency service. Call 609-665-3022.
Book online or call your local Trane HVAC team — same-day & 24/7 emergency service.
