severe clicking (relay type noise)?

I have come across this problem a few times, it is the relay on the pcb that controls the pump, there should be a delay after the boiler turns off before the pump stops, this is called pump overrun, intended to remove latent heat from the boiler. the control for this relay is not switching correctly and causes the relay chatter.
to remedy this problem you will need to replace the pcb

gary.wright53@googlemail.com
June 2007