| Armstrong Error Code | What this means |
|---|---|
| LED is on and not flashing | The furnace is operating normally |
| Single LED flash | Flame continues to burn when the gas is off |
| Two LED flashes | Problem with the pressure switch |
| Three LED flashes | Problem with the pressure switch |
| Four LED flashes | Problem with the high limit switch |
| Five LED flashes | Problem with the rollout switch |
| Six LED flashes | Problem with the pressure switch |
| Seven LED flashes | Problem with the ignitor |
| Eight LED flashes | The flame is dropping |
| Nine LED flashes | Problem with the voltage |