Worcester 240 erratic hot water

hi guys, Okay I have a problem and I cant find anyone else whos had the same one.
First of all I have a Worcester 240 combi which is at least 5 years old and has been very reliable. The fan and pressure switch were replaced a year ago when the pilot wouldnt light and learned a lot about the boiler then but right now it has me pulling out my hair.

Okay I have perfect C/H, the hot water is the problem. Turn on a tap, the demand light comes on,the switch makes contact and boiler lights up and I can see the gas light. after about ten seconds it cuts out again if I turn the tap on again quickly nothing happens at all. it doesnt recognise any demand. All taps in teh one bedroom flat work this way and sometimes the hot water stays on long enough to run for several minutes before it stops again. If I turn on the shower I get no reaction in the boiler at all. Last week the bath would run hot water and would stay on but now i\\\'m down to five minutes of hot water at the most and its getting worse. if I leave it alone for a while and then turn on a tap I get hot water it just runs out as its not heating any new water going through the system.


From what Ive read I think the problem is the diverter but before I change any parts I wanted your advice. Please dont say its the motherboard!!!!

It sounds like the PCB is doing all the things it's supposed to.
The boiler is reaching its HW temperature setpoint and switching off.

It sounds very much like the diverter valve diaphragm has a hole in it.

Replacement diaphragm, or complete new diverter assembly needed.

yeah everything works its just not staying on or recognising demand. is it easier to just replace the valve instead of the diaphram?

If you can get a replacement diaphragm, it should be chageable with the valve in place and without a drain-down (just turn off cold supply, I THINK).
But the manual only lists a complete DV assembly - dunno whether you can get just the diaphragm.
Ezypart lists a complete valve for 37.50 + VAT

Have you solved your problem?
We've had same problem for some time. Various cheaper parts have been replaced but still no joy.
Ours has been heating the water for a few minutes and it seems the water gets too hot so it cuts out.
We've now been told its probably the heat exchanger, which I haven't priced yet but its probably still cheaper than a new boiler.

u can change diaphram only but u will need some silicone grease and possibly a new set of washers. u also seem to be suffering from a scaled up dwh h/x.common on these boilers.

If you change just the diaphram you will need a socket to remove the stuffing box and replace the 'O' ring behind it, if you don't it will leak for £37 change the valve, lot less hassle. Yes, mains off and no pressure on heating side. Also, I think there is a slip coupling on pipe to the H/E change the 'O' ring in that as well

I have this feeling that you will be wasting your time only replacing the diaphragm!

But you will probably prefer to do that because its cheaper ( until it does not cure the fault ).

Tony

Yes as Eyesee said, there is a slip coupling, change it cause if ya don't believe me it will leak.