No hot water but central heating works on my Vaillant TURBOmax VUW 242E, 28?

Assuming that you have a GOOD flow of water through the taps, the possibilities are: 1/ The diaphragm has a hole in it 2/ The microswitch paddle has broken 3/ The microswitch is faulty 4/ The PCB has died.

1 and 2 can be checked by dropping the front panel and watching the paddle as an assistant operates a hot water tap. If the paddle doesn't move down then check that it isn't broken by touching it with the tip of a screwdriver - if it is broken it will be loose. If it isn't broken, then it's the diaphragm.

If the paddle moves down and depresses the switch, then change the switch. If this doesn't cure the boiler then replace the main PCB.

If you do not have a good flow of water, then descale the DHW heat exchanger.

Hope this helps.

Steve Bennett
July 2006

I have the same problem although my boiler is only 4/5 years old. when a hot water tap is switched on the demand indicator does not illuminate. So I was guessing that there was a flowswitch which detects that there is flow and hence the boiler needs to start.

So the message re the diaphragm has confused me.

Are there any proper boiler maintenance manuals out there.

Cheers - Kids have not had a bath tonight so mum is not happy.

Eamonn
July 2006

same thing happened to me. The engineer said that the water section needed replacement - 1 hour labour & part = £150. You can guess the rest - this hasnt fixed the fault & now they say that as it's 20+ years old I need a new boiler!

Anyone got any ideas?

David hopkins
June 2006

You may be able to, depending on how good you are with your hands! The diaphragm has perished in the water section at the bottom of the boiler. The diaphragm itself is about £3, but it is about an hour job to change it. Worst case, the water valve itself is KAPUT, and they are about £200.

craig, plymouth
May 2006