URGENT Valliant Boiler - pls help troubleshoot

[Ambienz]

Depends on boiler and type. If it’s the same as the EcoTEC pro Combi then it’ll be pins 3 and 4. Are you testing between a known Earth and the lives?

I have Live, Neutral and Earth and Pins 3-5 are switched live, so testing between the Neutral and Live pins

 

[Ambienz]

The motorized valves are external, zone valves and supply the switched live to the boiler which you say is live so would point to a boiler problem, you could switch off the CH and HW demand and check for no voltage on the switched live to prove it, when you switch it back in with either CH or HW demand listen for the fan starting up and check the d and s parameters again if no fire up.( and any f fault codes)

Yes. if it turn off control zones then I have no power to switched live and you can hear motorised valves retracting.

When switch live comes on there is no noise or action from the boiler, nor are there fault codes

 

[Deleted member 120897]

I have Live, Neutral and Earth and Pins 3-5 are switched live, so testing between the Neutral and Live pins

5 is a neutral connection. Also on these boilers, if the cover is removed it should be checked for safety afterwards using 26.9 of the gas safety installation and use regulations 1998. If nothing is firing up, then it could be the pcb, but I would engage with a gas safe registered engineer to progress further.

 

[Jerry]

Gut feeling is PCB
Time for someone registered.
Switch on your immersion and get some fan heaters