Vaillant Compact Combi not firing

[Kojak]

Does anyone know the firing sequence of the Vaillant Compact Combi (VCW GB 242EH). Ignition P.C.B has been changed A.P.S and fan are O.K.
Will not spark for heating or hot water. Not sure if any pump pressure or flow switches are relevant before ignition.....

 

[ChrisR]

Check pump is turning.
Check primary flow switch operating.

 

[weargas]

you need to know if gas is coming through even if it isn't sparking. If gas is coming through then it could be your spark generator.

 

[Kojak]

The pump is turning & both pressure switches are working, a yellow neon light & a green neon light illuminate when the pump runs. There is gas to the valve but none is passing through. Tried to speak to Vaillant tech support but was held in que for 50 minutes & then gave up ! AAAAAAAAAAAAAARGH!

 

[corgigazza]

1 does boiler lock out, red light come on

2 can you hear the inition sparking

3 is flow switch (black valve with 3 screws) on gas valve operating when the pump runs, this pushes a pin that lets gas to the burner.

4 burner lights on ignitoin gas rate this is sometimes set to low to give ignition.

5 check diverter valve micro switches x2

6 check water valve flow switch

note need corgi engineer to check some of these things

 

[Kojak]

The red light doesn't come on. Both Microswitches on diverter valve are working, the switch on the water valve is working too. There is no spark at all and no gas is passing through the gas valve. I will check the pin on the gas valve (I thought it had a solenoid!).

Thanks

 

[corgigazza]

this type fault is most probably caused by the ignition pcb, have the plugs on pcb been fitted corectly, is the pcb a recon .