Vaillant Turbomax VUW242e

[alinsons]

I am working on a Vaillant Turbomax VUW242e. This boiler runs through ignition sequence and the burner appears to on ignition rate for no more than 10 seconds and locks out, during this time you can hear the sparking in the combustion chamber between the two electrodes on the left.

I spoke to Vaillant and I disconnected the NTC in main combustion chamber still the same, I have looked for 5-20 volts DC on gas valve solenoid (white plug with two black wires from X100 on the circuit board) nothing! It looked like a faulty PCB is not sending the signal I have changed the PCB from another Vaillant Turbomax VUW242e. I have look for 5-20 volts DC on gas valve solenoid (white plug with two black wires from X100 on the circuit board) again nothing!

I have checked for continuity on the ionization sensor right side in combustion chamber and then changed the electrode. I checked for continuity on the two black wires to the gas valve solenoid also okay.

Not sure what else to do, unless I have 2 faulty circuit boards, I would really appreciate some helpful advice, I am also unable to locate a manual for this boiler.

[Ed Sirett]

Are you saying that the boiler actually lights for 10 seconds, albeit only at the minimum ignition rate? In which case the gas valve is probably OK (togethher with its driving circuits). My efforts would be checking the flame sense lead and electrode (again).

Also Check earthing and polarity of mains supply.

[alinsons]

Hi Ed

Thanks for the resp> >