A1 checks
| Step | Check | If yes | If no / next |
|---|---|---|---|
| 1 | System pressure below 1.2 bar? | Power off. Check for leaks and repair. Fill, bleed, and re-pressurise. Turn on. If A1 remains, go to step 2. | Go to step 2. |
| 2 | Pump seized or sticking? | Free / release the pump. | Go to step 3. |
| 3 | Audible bearing damage on the pump? | Power off, isolate, drain, replace the pump, refill/bleed, reconnect and turn on. | Go to step 4. |
| 4 | Activate the venting sequence | In the first service level, set service function 2.C (air purge) to 1 and store. The boiler vents for about eight minutes. Vent radiators manually. |
Gas work stays with a Gas Safe registered engineer. These steps are guidance from the manufacturer sequence, not a substitute for the handbook.