Autofill not triggering the pump

[Duncan Slarke]

I have a single group Compact A. Everything seems to work fine except the pump will not trigger on low water level. There is a buzzing - and the mains water pressure slowly fills the tank - so I assume the solenoid is opening. But no pump. The pump works fine to the group. The manual fill works fine but much more quickly. It was always the case since I bought it second hand.

I’ve tried attaching a different level gauge - as I had one - and disconnecting the motherboard and reconnecting. It didn’t look obviously modified. But the same.