Msmk0 Ok, unbolted everything again and checked all connections and all seem
fine.
You didn’t say, if the boiler is heating or otherwise. I assume the two spade-like wires are connected ok at the bottom of the boiler. If it is still not working, I think you need to contact ACS again. Let’s wait for @DavecUK for any other pointers.
Msmk0 About the nut bolt in the group, I don’t understand how this is related since I didn’t ever touched it. It is at factory settings, so issue of the regular little pump engage has to come from somewhere else.
The pump for the group engages only when there is a contact with that metal pin. Over time, it can change its posture as we operate the lever. Too tight a contact, the pump will start kicking in. Depending on the duration, you may or may not see a few drops of water thru’ the group. Do you get water drops through the group when the pump runs a bit? Please try, lossen the nut and see if the problem goes away.
If it doesn’t stop the issue, then another possibility is if you have removed the water tank and put it back, it may be trying to prime the pump. It will be a continuous process until the pump is primed (~= the liquid forces all trapped air, and vaccum out). You may have to manually prime the pump to fix this.
