dodgy pcb`s

[lagunaglen]

Just spent best part of a week chasing faults on a worcester 24i junior (older standard efficiency)
Not a full week, just an hour here and their.
Previously over the last few weeks
1st visit -aps,and fan diagnosed and replaced, leftboiler working.
2nd visit-nothing working, noticed aps had started to melt underneath and the T piece on rubber hose between aps and fan had melted and wiring to overheat stat and aps melted to boiler casing,
but no other signs of excessive heat,hoses in tact etc, phoned tech , new pcb diagnosed, new pcb, aps and T piece fitted, plus wiring loom.
Turned on , nothing at all.
Phoned tech , pcb they say, phone merchant who says bog off, but agrees it does happen and replaces it.
Fit even newer pcb, turn on , no pump but hot water,its a start i suppose.
Phone tech and check everything possible,again, pcb he says.
Phone merchant who says he doesnt believe me but he has one more in stock and as we are such good cstomers, etc, plus i say tech say to me that he needs to phone them to explain situation.
Fit new pcb, bugger me it works, just 2 aps 1 fan 3 pcb`s oh and i forgot an overheat stat later.

Anyone else had to change 3 pcb`s, i know this sounds like im a parts changer but im not, if im in doubt i always phone tech support , but our firm own the houses and dont like changing boilers if can be avoided.`
I personally would like to condem more but if its less than about £350 to fix they do this instead.
Is there anything more frustrating than a faulty pcb?

 

[namsag]

Nothing worse than diagnosing a fault properly and then the new bit is also feked . You know in your gut you have it right but starts getting you thinkin whet the F have i missed.

 

[lagunaglen]

Yeah , namsag, knew i was right but merchants start can start insinuating that you have buggered up the new part.Luckily we have a great merchant who wil letus try a take another spare if we think one is faulty as he knows we wont screw him over.

 

[simond]

Thats very interesting.

We were called out to an iJunior showing some wierd error codes.

Worcester said change the PCB, definately the PCB. So we changed it - nothing.

Found the APS had melted. Changed the APS. Boiler fired up, no error codes.

Billed the customer.

Next day customer rings back, boiler failed. Had someone else round, they had changed the PCB, boiler now OK. She implied we were idiots and wanted all her money back including the APS.

 

[lagunaglen]

sounds like a similar scenario to mine simond.Tech suggested that the pcb failure could have caused fan to stop running but the boiler did not shut down until sometime later when things had started to melt.

 

[BertieGas]

had just the same fault on a 28i junior. melted fan pressure switch and tee piece. replaced both and just about to pack up and go when the burner lit with NO demand for heat or water, and the fan not running. it was the pcb, but a scary fault.

 

[lagunaglen]

Our other engineer has just come accross another one today, melted aps and tee piece, but rubber hose to fan and aps look ok.
Check wires along front left side to aps and o/h stat as mine had melted together and stuck to casing.

 

[superdupergasman]

the pcb's are a bit iffy on that range, the 28si mk II is bad too.

the old myson midas air flow sensors were far worse....I fitted 5 in a row once before getting a working one, then got a reduced price boiler after moaning to potterton.

 

[Kristoflampie]

Couldnt agree more, all that range thro Si, Si2 , junior all use similar range of pcbs, have witnessed the flame lighting up with no fan running a few times. Its the relays sticking as APS is relaxed on ignition phase and only makes when fan speeds up for high flame, in short, ignition can occur with no air pressure switch signal. Tapping the white relays at the bottom of the board unsticks them and pcb works okay for a bit. Sometimes you can get fan running away on high speed but no ignition , back to front version of the problem, either way pcb,s in these boilers are a joke.

 

[Corgigrouch]

Aaahhh... Si Mk2... Only got one customer with one of them and the circuit board dies every Christmas... Fortunately Parts Centre replace it under warranty. Last time the boiler wouldn't spark up but the fan ran constantly, changed the board but the fan wouldn't run, swapped the old board back and the fan was dead, checked the coils and this confirmed the fan was duff, just a coincidence I guess unless the fan was on it's last legs and took out the board or did the fan die because it was running constantly?

Either way the Si 2 was not a good boiler.... The things folk buy on Ebay

 

[daverogers123]

I find many of these problems are caused by the control board, microscopic cracks in the solder joints causing connection issues particularly where the board connectors are soldered on, and especially where high currents are switched (like the output power to the pump, which if it doesn't get power will cause an overheat condition)

And PCB subjected to temperature cycling is prone to joint cracking, particularly now after lead was banned from solder in 2007. making joints more brittle.

I've found that 9 out 10 boards faults can be repaired by re-soldering the joints.

Hope this helps.
Dave Rogers

 

[Boilerman2]

I consider the older Junior to be potentially dangerous as a faulty pcb can lead to some very unsafe situations i.e. burner firing up with no fan running pumping mega CO out and melting everything inside the case
I thought controls on gas appliances had to fail safe, these boards certainly don't!!