Worcester 24cdi Hot Water Gradual Fail

[fordfocus2003]

Hi all,

Hopefully this is a fairly quick question that someone may be able to answer in diagnosing an issue with my Worcester 24cdi combi boiler.

Recently the hot water has stopped working in my flat. Water still comes out of the hot taps, at the same pressure as before, but it is no longer hot.

I think the issue is in detecting whether the boiler needs to heat the water; when I first spotted the issue, the boiler no longer heated up the hot water when i opened the tap slowly, so had to open the tap further to make it fire. The next days, it would then not heat the water at a medium pressure so I had to open the tap even further for the boiler to fire. The last couple of times I got hot water I had to have the tap on full pressure, splashing the walls, as this was the only way it would fire. Now I get nothing...

This failure happened over the space of a day or two.

If it helps, when I run the central heating, the water will come out lukewarm for a short while, but Im guessing this is because it's being heated a little by the other side of the system.

I've read multiple things about flow sensors and diverter valves, but read nothing about this specific gradual failure type so hopefully that should give a clue to what's up,

Thanks a lot

 

[Terry7556]

under the boiler is a line of copper pipes. does one of the fat ones (22mm) get hot when you turn on hot water and does the tap symbol light up when you open a hot tap

 

[fordfocus2003]

hi, thanks for the reply,

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• fordfocus2003
• 5 May 2014
• 1

The bright red hot water light has always been consistent with the sound of the boiler firing, and hot water coming out of the tap.

Now when I open the hot water tap fully, the boiler doesn't fire nor does the red light glow.

I just kept the hot tap open for a while, the hot water red light didn't glow, the boiler didn't fire and none of the fat pipes (A, D or E) got warm.

thanks,

 

[fordfocus2003]

I've just been doing some further testing after reading this thread. //www.diynot.com/forums/viewtopic.php?t=117464

The micro switch attached to the diaphragm is working fine, as I pushed in the micro switch with an electric screwdriver and straight away the hot water light lit and the boiler fired.

The diaphragm shaft does extend out of the casing when the hot water tap is on full, but probably only by around 4mm max. The micro switch casing is very loose and also moved freely in the same plane as the direction of extension for the shaft, so there could be a problem with the micro switch being held in position also.

Thanks

 

[45yearsagasman]

The diaphragm in the diverter valve is failing. Cheap part, but a tricky job to do due to difficult access.The micro switch should beheld in by a circlip.
http://www.newtonnet.co.uk/house/boiler/

 

[fordfocus2003]

Thanks a lot for the reply, my logical brain says it must be a diaphragm issue above the sensor, as although it extended whilst the hot tap was fully open, it appeared to not move under smaller flows, so suggests root cause.

Thanks loads for the replies, I've learned a lot, good to know where the issue begins before working out a plan to fix it. Now off to diagnose the washing machine fault which broke down at the same time...

 

[St0rmer66]

Diaphragm is an absolute b*****d to change on these boilers!

 

[fordfocus2003]

Today is repair day!

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• fordfocus2003
• 16 May 2014
• 1

The next job is to remove the diverter valve from the system. I have removed the relevant screws & clips, loosened the connection to the pump and released the bypass tube, but the diverter assembly seems really firm on.

Is this normal? There seems to be no movement, and it feels like if I pull / move any more the whole boiler will come off the wall! Does anyone have any tips or advice for removing this part?

Thanks a lot.

 

[St0rmer66]

You need to undo the 4 screws holding the plastic part on the left in. You can't move the brass section to the right to disengage said plastic part until the whole lot has been pulled forward first (the back connection on the brass part is still into the cold isolation valve). Often it's easier to just remove the whole lot and then separate the two parts but I often leave the bypass pipe in as it's such a pain to get back in (seriously, good luck!).

 

[fordfocus2003]

Thanks for that Stormer, managed to get it off in the end, by levering it away with a large flathead screwdriver. Due to length of service, there was a lot of build up around the joint, where it had partially seized...

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• fordfocus2003
• 16 May 2014
• 1

Happy to report it's back in, although now I have the challenge of pushing back in the bypass pipe - any tips?!? I'm guessing it's just a job of pushing in as best as possible until the joint is made? Thanks

The story so far...

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• fordfocus2003
• 16 May 2014
• 1

p.s. here's the state of the diaphragm in case anyone's interested, so that was definitely the problem! You can see the main tear top right which was 7 or 8mm wide and 3 or 4mm high.

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• fordfocus2003
• 16 May 2014
• 1

 

[fordfocus2003]

Still really struggling to get the bypass pipe in. It's seated within the plastic manifold, with a new o-ring and some silicon grease, but just can't push it in enough to get the clip round it no matter what I try. Does anyone know of any tips? Thanks a lot.

 

[picasso]

The bypass tube catches everybody out (including me) have a look here.

http://www.newtonnet.co.uk/house/boiler/

 

[Dan Robinson]

Yeah - that flocker got me on the last one.... then the cold water inlet oring leaked so I had to take the bloody thing out again

Great bit of design innit .

Still got there in the end.

 

[picasso]

Started to feel suicidal on the last one I done as I watched the ****ing leak even with all new washer ,silicon, o rings ect I now refuse to change the diverters on these boilers.

 

[mogget]

My 26CDI XTRA died by leaking from nearly every joint. I left a bucket under it for quite some time while I saved up for a new boiler.