Worcester 28cdi - "fail point J"

Postby jim the plumb » Mon Dec 20, 2010 8:23 pm

Hey Guys,

Can anyone help me with this fault?

Worcester 28cdi - it started with a seized fan.

I replaced the fan and the silicone hoses which were cracked. All good or so I thought.

A week went by and "Fail point J - flashing hot tap light" - occured, which is an air pressure fault.

I found some condensation in the silicone tubes and cleaned them out - All good.

3 days later had the same fault again so I checked the air pressure switch and ended up replacing it.

A week has gone by and it has failed again - it resets itself and the boiler runs as normal for a while - Worcester were unable to explain it after going through the full diagnosis and fault finding with me on the phone.

I remember that once on a council contract the same thing happened on a 25cdi xtra - they replaced the flue, fan, air pressure switch, PCB and ended up replacing the boiler cos they still couldn't fix it. The only way it would run was to leave the negative tube off the APS.

Another call to Worcester I was told that the thermistors may be faulty and the heat exchanger fins might need cleaning. I think he got the wrong end of the stick as the fault is always " Fail point J" - Air pressure fault and not lock out overheat.

The flue is clear, Fan/ Air pressure switch is new. Can anyone point me in the right direction?

jim the plumb
Posts: 38
Joined: Sun Sep 28, 2008 7:52 pm


Simply Build It

Postby htg engineer » Tue Dec 21, 2010 9:21 pm

Are the case seals in good condition ?

htg engineer
Posts: 3219
Joined: Tue May 22, 2007 5:22 pm

Postby jim the plumb » Tue Dec 21, 2010 9:42 pm

Hi htg.

Yeah seals are good. The boiler looks brand new.

I rang my old boss this morning - ex british gas engineer.

He told me that the light also flashes when the flame rec, and/ or spark electrodes and their harnesses start playing up. He didn't even have to think about it. Just said it straight away. I hope he's right, cos there's no way I would ever have gone down that route! What do you think?

I replaced them this evening - once again it'll be a waiting game until i get the dreaded text. "Sorry, it happened again".

jim the plumb
Posts: 38
Joined: Sun Sep 28, 2008 7:52 pm

Postby jim the plumb » Mon Aug 15, 2011 4:51 pm

Hi guys,

Its been nearly 8 months since I posted this fault.

Well, I can safely say he was right.

I haven't had a callout since on this boiler and it's running fine.

Add this one to your list of diagnostics for Worcester boilers.

jim the plumb
Posts: 38
Joined: Sun Sep 28, 2008 7:52 pm

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