Written on: 27/04/2013
I was working today on a Baxi System 100 HE Plus. Boiler fires up and working fine till reaches the set temperature, goes off, cooling off period, fires up again and burner goes off and on, off and on every 3-4 seconds without lock out or any error flashing lights.
I have cleaned the ignition probes, replaced the temperature sensor, both overheat stats, checked the wires ok.
At the end i have taken off the boiler outlet flue elbow and realised the inner flue seal/O-Ring had been burned out, vanished,causing products off combustion geting back to the fan, sucking in back to the burner causing lack of the air and makeing boiler cutting off and fireing up again and so on without lock out or errors flashing lights. Simple as replaced all flue seals and boiler working fine, smooth and quiet. Co/Co2 ratio 0.0008, perfect. Problem sorted without replacing PCB or Gas Valve or Fan,originaly adviced from Baxi to replace them.