Worcester Bosch Greenstar 35CDI not pumping

[mayurw]

So we've had this boiler for around 12 years and recently it developed a leak from the internal filling loop, the sort that you had to insert a plastic key into. Anyway, had look on the net and brought a new keyless type and fitted that over the weekend. Ever since then, when the heating is called for from the programmer, the boiler heats up as you see the temp rise on the screen but the pump doesn't run! When I initially turned the boiler on after replacing the filling loop it came up with the inverted 'h' on the screen which I let run through. If I switch to the chimney sweep mode, heating works for a while. I've also tried resetting the boiler but it's not helped. Any ideas?

 

[Madrab]

There is a basic start up procedure when it comes to fault finding and the sequence of events would normally be - call for heat > pump runs > flow switch ok > fan runs > pressure switch ok > gas valves opens > sparks and lights > flame ok/stabilises - boiler keeps running.

So the pump is usually the first thing that kicks in and if it doesn't then the rest of the sequence shouldn't run and the boiler wouldn't light. Your boiler is running, so normally the pump wouldn't be what's at issue. Also if it runs in service mode then that would also suggest the pump's ok. Does the temp climb and then the boiler shuts off? Is the auto air valve open, pump been bled? I presume the flow and return are open if the CH works for a time

Another side question, who performed this work? As it's a room sealed outer case, it really should be a GSR engineer doing the job.