Heater is burning very strong and control valve will not shut it down. I have replace the following:-
Control Valve, Mag valve, thermo coupler.

It starts and runs for a minute and then it shuts down totally. The ony way I can get it to run is to take out the heat sensor from the left hand side of the unit and keep it away from the unit it will then run on contiuously. Please can you help

John Mclennan, May 2009