Combi Potterton Puma 80 mains cut out

[tonyid10]

Coming home from work to find the boiler has stopped working. Fuse F1 on the Printed Circuit Board (PCB) has blown - Inspect the PCB to find no other suspected faulty components (the local engineer had resoldered a dry pin around 18 months ago).

Replace the fuse; check the pressure gauge (at 2); on the control panel,
set the boiler switch (DHW) to standby and CH switch to off.

Switch on the boiler - fan running (at slow speed) but as soon as I
turn the DHW from standby to on, the fuse goes. Replace fuse and try again but this time turn CH on first - no response; try turning on the DHW
and the fuse blow like previously.

The Fault Finding flow chart (electronic) in the menu suggests checking for a short circuit on pump, mains transformer, fan and gas value solenoids but I am not sure how ? Can some one help please ?

Any other suggestions is also much appreciated.

tonyid10.

 

[LUNAT]

HI

it sounds like faulty gas valve.

 

[bellairaphon]

Id also have a look at the dhw microswitch sounds like its stuck and may have water in it.

Nath

 

[Agile]

Disconnect the pump at its plug but from what you have said that should not be the fault but is usually the most likely component.

Also look at the LP water switch ( if fitted ) just in case.

The gas valve only fails if the AAV leaks on to it. The AAV is strategically placed immediately above the gas valve. Thanks Potty, that gives us a job a year.

Tony

 

[tonyid10]

Thanks LUNAT.

New update - after a chat with a friend of mine, who suggested getting a multimeter for the job. I am looking for a meter that is easy to use, any suggestions please ?

Pump stuck ? unscrew, rotate then screw back the 'hex knob'. Replace another fuse and this time, no problem when switching the DHW from standby to on. However, on tunring on a tap, the gas burner fired up for about 5 seconds then the fuse went. Checking the manual to find nothing
helpful to diagnose the problem. Any suggestions out there please ?

Thanks all.


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more updates -

Gas valve - no sign of water leak on it; all wire and joints appear OK though a bit dusty.

AAV - the cap appears tight but the manual says keep it loose. I slightly
loosen the cap and water starts to come out; to avoid making things worse,
I screw the cap back to its original position. How loose should the cap be ?
Can this be the cause of the mains cutting out ?

Microswitch - electronic joints appear OK, the little spring seems OK too.
Any simple trick to test this further ?

Thanks.