When the hot tap is run or the heating switched on, the boiler ignition continues to spark, but the boiler does not ignite. On the front panel, the red fault light does not show any fault (illuminate or click out), the amber light illuminates followed by the green light. Having had the boiler checked by an electrical engineer, there appears to be no problem with gas supply,fuses or fan. Can anyone suggest anything.

Many thanks in anticipation of your response

Chris Jones, January 2007

After the hot water tap is closing, ignition spark starts again. After cca. 15 sec. the red light switch on. The problem appear more and more frequently, but not every time. Any ideas ?

Damjan, December 2012

If its not sparking and the electrodes and HT leads are ok then check the differential pressure switch across the pump is operating its micro-switch, as this can hold off the igniter coil and stop it from sparking.

R Dexter, August 2012

Just bought a house & I'm experiencing simialr problems. At first the hot water wouldn't work when the heating was on & that's been fixed by replacing a divertor (?) valve. However now the heating is really temperamental and I have to switch on the hot water to make the heating go on. Does anyone know where I can find a Vaillant boiler engineer in Manchester?

Jo, January 2007

ther is a small servo valve fitted to the gas valve make sure this is operating otherwise it will not allow gas thru the gas valve

dave, January 2007

If memory serves me correct, on this model the red indicator is at the top for burner lockout...

As such, yes... It is controlled by the PCB.

GasAid.co.uk, January 2007

Does the PCB board referred to, drive the red indicator light?

Thanks for your quick response

Chris, January 2007

You need a Heating Engineer.

Possibly gas valve failing to open allowing low rate gas into the burner to ignite or PCB not sending voltage to gas valve in the first place.

GasAid.co.uk, January 2007