Baxi solo 3

[Carlosfandango]

This is long shot but worth a try. Went to the mentioned boiler as the pump overrun was running continuously. Everything pointed to the pcb so I replaced this with the same model. It worked correctly when I fitted it ie. The pump shut off after roughly 5 mins. The customer called today to say the pump is running all the time again? Anyone know what may be causing the pcb to fail like this?
The system works as it should and there is only a switched live when the valves open before anyone suggests a faulty valve.

 

[Megavolt]

How long ago did you fit pcb.

 

[onions1066]

Have you looked at the schematic? What triggers the pump overrun. Possibly a sticking flow switch?

 

[Carlosfandango]

Not sure what triggers it. The boilers instructions are missing so I'll need to see if I can find any on line. It's quite an old boiler. Just thought someone might have encountered the same problem. Seems funny that when the pcb was changed it solved the problem for a few days?

 

[davesparks]

That suggests to me that you have disturbed a faulty sensor when changing the pcb and inspired it to work again for a couple of days.

Do a bit of searching on the web and see if you can get the internal schematic. That will reveal if and what sensors there are in there that could be responsible.

 

[Carlosfandango]

Went back to the boiler today to find that the motorised valve was faulty and was keeping not just the pump on but the boiler too. Purely coincidence and here's me doubting my fault diagnosis!

 

[davesparks]

But you said in the op that the valves were working correctly.

 

[Carlosfandango]

They were when I originally went to the job. Firstly the overrun pump was running continuously so I changed the pcb. That solved it but the customer phoned the other day to say it was doing it again, but the boiler was running all the time too!