heating fine , but wene i run hotwater it goes to full burner and shortly it goes to low burner thus colder water , engineer has swapped thermister/ modulator/ diaphram, and now thinks its the pcb!! , can you help , hes mentioned gas presssure fine on heating but fluxuates on water side . regards andy

andy galbraith, December 2007

yes its going to low flame , im planning to clean up exchanger and venturi pipes tomorrow , any tips ?

andy galbraith, January 2008

It doesn't take long to remove the domestic heat exchanger, this may be blocked.

Big A, December 2007

Are you sure it is modulating down to low burner and not cutting off and going to pilot?. Does the flame go down with a click from the gas valve?.

c, December 2007