"Ed Sirett" wrote in message on.co.uk...
On Sun, 09 Nov 2003 05:22:31 +0000, Ian Nutt wrote:

"Ed Sirett" wrote in message on.co.uk...
On Sat, 08 Nov 2003 09:50:44 +0000, Ian Nutt wrote:

I have a Vaillant combi boiler and seem to have a problem with the
diverter valve. The hot water only comes on when the heating is on. I
have taken the diverter valve out of the boiler to study it and can
see that the diaphram is supposed to push up a pin that forces a
hammer to fall and make a contact that ignites the burner and diverts
water into the hot tap system.

When I turn the hot water tap on you can see the hammer try to move
down to make the switch contact, but it does not have the energy. It
would seem that there is not enough pressure to push it hard enough.

Does anyone out there understand what i'm talking about, or, even
better, know what the problem might be?

Which model? They work by very different mechanisms.

Ed - thanks for getting back. I don't know! Cannot see a model number
written anywhere and have no documents on it. Do you know how I can
identify it?

Please describe the general appearance - eg. grey/black/beige control
panel. Permanent pilot or electronic ignition? Fan assisted flue or
balanced natural draught flue?

Anyway from the description is it most likely a split diaphragm in the
water flow sensor.

If you look around and perhaps remove or swing-down a panel you will
likely find the model type and rating plate.


Ed,

I have taken the right hand side panel off and there is no
identification plate visible anywhere, just various stickers with
nothing that looks like a serial number. The pump has 'Type VP5'
written on it, but I assume this refers to the pump.

The control panel is black, with green dials and a pressure gauge
bottom right. There are 4 dials (on/off/relight, water temp, ch temp,
function setting) and 7 indicator lights that light up green to
indicate when the burner is on etc. It is electronic ignition and
naturally vented flued I think.

I took the brass diverter valve out over the weekend and took it
apart. There was a water chamber above and below the rubber diaphragm,
and the diaphragm didn't look out of shape. There is a pin attached to
a plate which is supposed to push up when the pressure of the mains
water is released. I made sure it was loose enough, and refitted it.
It didnt do any good - when the hot water tap is turned on you can see
the hammer try to fall to make the electrnic circuit that will ignite
the boiler, but it is obvious that the pin inside is not moving up far
enough to push this little white plaster hammer down to make the
circuit.

Does this sound familiar?