Vailant ecoTech plus 831 No CH flow

[The1GDP]

Hi, Ideas welcomed!
Drained down system, changed radiator ensuring correct flow direction for TRV, refilled system, bled new and existing rads, restarted boiler, confirmed thermostat heat demand, boiler fires up, flow pipe gets hot, no apparent flow to system, no heat to pipes, DHW flow correct, no faults evident on display, following day partial drain off hoping to clear any air blocs, refilled, exactly the same symptoms!
I’m lost for any additional actions that might resolve……..

[Someone-Else]

What about the pump? does that need bleeding?

[aeromech3]

No fault codes showing ? It shows correct pressure? Not sure if this applies to your model/year, but taking it as a combi.
Bleed the heating pump by loosening the central screw. Close the filling valve and the cold water dispensing valve. Be prepared with a towel and a plastic container.
• Loosen the cap of the pump A.A.V. (automatic air vent)(the appliance is ventilated independently by the pump A.A.V. during continuous operation).

[sammy.se]

Sounds like it could be the diverter valve?
I bought an original new one from ebay very cheaply

[Someone-Else]

It is always best to establish what is causing the problem, changing parts at random/guess can be expensive and rarely works.

[gas4you]

When you turn the boiler on can you hear the diverter valve moving?

[sammy.se]

I recently had my diverter valve changed, hence my suggestion. @gas4you, it's that part the sounds like rapid clicking/door creaking (ish), right?

[gas4you]

yes

[sammy.se]

If the OP is sill monitoring this thread, tell us what you hear when the boiler starts. Does it click/creak?