A7 checks
| Step | Check | If yes | If no / next |
|---|---|---|---|
| 1 | Is the water NTC connector corroded, damaged, or dirty? | Replace the affected parts. If A7 remains, go to step 2. | Go to step 2. |
| 2 | Power off, unplug the 20-pin PCB connector, and check resistance from connections 3 to 4 on the cable side against the NTC table. | Note service settings, replace the PCB, restore settings. | Go to step 3. |
| 3 | Unplug the NTC and check its resistance against the NTC table. | Replace the 20-pin connector lead assembly. | Replace the NTC sensor. |
Gas work stays with a Gas Safe registered engineer. These steps are guidance from the manufacturer sequence, not a substitute for the handbook.