Main 24 HE cycling on and off after replacing Honeywell v4073

Good Morning All

I really hope you can help. Yesterday we woke up to find the central heating not working. The hot water would turn on but the heating would not. The heating would only turn on if the hot water was on.

I finally pinpointed the issue to the Honeywell v4073a valve. So I bought a new valve and replaced only the power head. Then rewired it into the junction box which also has the nest wiring.

The heating will now turn on, as well as the hot water. Job done?! No....

I don't know if this is an issue I have caused or one I have not noticed but the boiler seems to be cycling.

I set the heating or hot water to on/max. The boiler turns straight on, but it will only stay on for 1, 2, 5, 10 mins and then the burner will go out and the light will flash. It will then switch its self back on in 1, 2 ,3 mins and continue on this cycle.

I'm assuming that's not normal? Help is greatly appreciated.

Regards
Philip

Does this happen when CH and HW are heating up or when house is up to temp? Are TRVs shutting down flow to rads? Do you have a bypass rad and another provision for bypass? Are these open enough? Is the pump running properly? Try different speeds on the pump. Check for blockages in the system. Is it clean or dirty? Air in the system?

Beyond the above, you'll need an RGI.

And your boiler is???

Thank you so much, lots of questions.

This happens from the moment o turn on heating or hot water, when not up to temp.
I'm not sure what to look for regarding the bypass rad.
I don't know where to find the pump?

The boiler is condensing main he 24.

The strange thing is that the flashing light isn't indicated as a fault it's part of the normal sequence section

Ok found the pump it's a grundfos red pump. And the wiring does goto the same junction box I rewired the power head into.

What does a working pump sound like? I can hear water passing through it and it's vibrating a bit but not much else..

When i switched off the heating it stopped vibrating so seems to be fine?

The switch is on 2 and I'm reluctant to change it presuming it was installed correctly on 2

Airlock

Thanks Tomy, how do I clear the air lock and where should I start?

Ok so this morning all I have done is change the pump setting from 2 to 3 and back to 2 then 1 etc. I could feel the pump working more and less.

I then set it back on 2 and left it there. Since then the heating and water have been on for 12 minutes without interruption. Does this sound normal or not? Is it now fixed!??

Nope after 14 mins it went off...

Just went round checking all the rads and found one was off. I've just turned it on, doubt that's the issue but keeping an eye on boiler again

Nope still on and off

Drain some water out of the system into a clear container and post a photo of it on here.