Does the Switch Control PCB fail often?

I suspect I might have a faulty Switch Control PCB.

A couple of resistors have got pretty hot and have scorched the PCB around them...is the usual?

The Store pump, which seems to be running constantly, is controlled through one of the relays on this Switch PCB, which is the Manual override, or SWITCH unit. The client tells me they have switched this over a number of times and I am begginning to suspect that this may be the culprit and the relay swicthing contacts have stuck or 'welded closed' keeping the Store pump running permanently.

Reasonable assumption or am I barking up the wrong tree with this one?

Expensive board too at around £80 for a couple of relays, diodes, capacitors and a few resistors!

Well what ain't expensive these days!
More to the point why is the owner using the "switch" that often?
Mike
MGC/H2O
Norfolk

Mike, the reason this customer is using the switch is becuase of my other post on this fault - about the HW tap running scalding hot, then cold thereafter....

We traced the cabling back up from the store pump and it goes into the switch pcb, which has the scorch marks around the resistors, which is why we are suspecting this board may be the culprit.

Your help in diagnosing this fault would be really appreciated, Mike, if you wouldn't mind having a read at my first post on this fault?

Cheers

Hi,
Can not find your other post.
But if really stuck, get in front of the unit.
And call Gledhill tech guys.
60p per minute but would help you a lot.
Mike
MGC/H2O
Norfolk.

Hi Mike,

My other post is:-

https://gledhill-repairs.forumotion.net/t1088-hot-water-runs-hot-for-30-seconds-then-goes-cold-whats-happening-how-do-i-fix-this-one

Pete

Hi,
Just read your post.
Who fitted the new ACB board?
Mike
MGC/H2O
Norfolk

Mike, it was an independant local plumber who did not fill owners with any confidence whatsoever and left saying he couldn't repair it! He fitted the ACB, changed the DHW sensor and tightened a few connections.

I live across the road from the house where this is and have gone in basically to help them out as they have had no quantity of hot water for some time now. All the houses in our street have the same Gledhill system2000 unit fitted. I have just checked the logical things such as LED error indications following the manuals' guidance on this and visual checks over what I can see, along with following the wiring diagrams in the manual. We did however take out the Swicth Control Board to check it after isolating the central heating as we could see that the resistors had got pretty warm and burned the pcb. Electrical checks seem to show all ok though.

My profession is an electronics system designer and engineer, so have followed fundamental fault finding processs with this, but I am not a plumber, so can only do so little.

Any ideas of what can cause the sypmptoms that are apparent?

Thanks.

Re install the PCB.
Have you the manual?
Mike
MGC/H2O
Norfolk