Just a quick update after following @DavecUK descaling instructions. To rinse out the descaler, i emptied and refilled the service boiler several times (as the water was quite grey). At no point did i observe the pump-running-on issue during the process. Then, this morning i switched on the machine and, again, no issue. However, a little while ago, the problem reapppeared. This is what i did:
I switched on service boiler and waited for it to reach temp.
I extracted some water from the hot-water wand to warm the cup.
This triggered a short auto refill of the service boiler. No problem so far.
After about one minute, however, the pump started again and did not stop until i extracted some steam from the steam wand.
Having observed more closely, it looks as though the water to the tank is not actually coming from the steam-boiler safety valve after all. Instead, it appears to be coming through the OPV. It is also at about the same temp as the water in the tank. So, my guess is: something is calling for a refill; however, the brew boiler and steam boiler are already full (so all valves are closed). As the water has nowhere to go, the OPV opens and lets it through. If this is correct, the water is simply being pumped from the tank via the OPV and back to the tank again. Does that make any sense?
PS BB has just come back with the following suggestions:
- take out the level probe examine and clean, as necessary. [should be fairly simple]
- check how close your micro switch is to the brew lever. This could be false triggering. [this I don’t understand]