| 607 | Flue pressure switch ON with fan OFF (pre-ignition authorization). | The air pressure switch indicates closure before the fan starts (contacts stuck, pressure tube pressed/blocked). Check the continuity of the pressure switch and ΔP at the intake/exhaust ports with a differential manometer (~0.47 mbar at maximum power) and inspect the tubes. |
| 608 | Flue pressure switch OFF with fan ON (does not authorize ignition). | With the fan running, the pressure switch does not close due to a damaged diaphragm, blocked tubes, or incorrect adjustment, causing the PCB to lock due to lack of approval. Check the electrical closure of the pressure switch at start-up and ΔP with a differential manometer; inspect the pressure switch hoses. |
| 6P1 | Air pressure switch delay. | The pressure switch takes time to close after the fan starts (dirt/sticking of the micro, leaks in tubes, or insufficient ΔP). Check the closing time and ΔP during start-up with a differential manometer and multimeter. |
| 6P2 | Air pressure switch opening. | During operation, the pressure switch opens (pressure drop) due to partial obstruction in intake/exhaust, leakage in tubes, or a defective pressure switch. Check contact stability and ΔP under load; inspect and replace the pressure switch if it does not maintain state. |
