Potterton suprima 50 flashing red light + noisy myson pump

[razor38]

Hello
Could someone help me fault find what is wrong with my system please?
I have a Potterton Suprima 50 which is given us a lot of trouble since January. It now trips out everytime it comes on and give us a flashing red light. In order to get it running again, I have to press the reset button. This however requires repeated action as it doesn't always stay on. Just trips itself out over and over again until I can finally get it running again.
I also have noticed that the when the boiler trips out, the myson pump in the airing cupboard stays running and rattles a lot. If I switch off the power at the mains, the rattling stops, but comes back again as soon as I switch mains back on.
I would like to know if I have the usual PCB problem and/or if it's my noisy rattling myson pump which is causing the problem?
Can anyone help?
Thanks

 

[heatingman]

New PCB req and a decent pump, get system checked over for design/install defects.

 

[baxpoti]

It's more likely to be a sticking gas valve.

 

[razor38]

I've bought a new pump as it's been noisy for a while now. This one:
http://www.screwfix.com/prods/57506...ing-Pumps/Grundfos-UPS-15-50-Circulating-Pump
grunfos UPS 15-50
Just went to fit it and found that the two big nuts holding the current pump in place are firmly stuck. Could not even begin to loosen them. I suspect I'm going to have to contact a plumber to come and drain the system in order to release the pump from a hight point on the pipe (but then can't isolate, so have to drain )
I've also taken the pcb out to inspect the soldering joints. They all seem fine. No sign of burning on the board (this happened to one of my neighbours)
If it's a stuck gas valve, is that a easy/cheap fix?
Thanks for you help

 

[razor38]

oh no. Now the heating/hot water refuses to start. Tries to light and fails every time. The pump in the airing cupboard won't stop running (have not fitted the new one yet)

The pump seems to really be struggling now so suspect it could be this

 

[twgas]

rattling pump could well mean its dry, check for water in system