"Paul King" wrote in message
news:1097786351.2BWD3IA2pSU1qusXQkAzqQ@teranews...
Wainscotting wrote:
When heating is on it takes an age to draw hot water. The diaphragm
is new so what else could be the cause? The boiler is about 15-20
years old (VWSine).

I used to have a Vaillant VCW25 Sine which did this!
If yours is this type, You'll need to take off the front door, boiler
'stat
knob, front panel and left hand side panel to get at the DHW flow switch,
which is at the rear of the boiler, low down on the left, behind the
"silver
tank" which is the DHW heat exchanger. As another poster has said, the DHW
flow switch operates a couple of microswitches which fire up the boiler
when
hot water (tap) is required.

In my case, the actuator rod had become very stiff through time and was
hardly moving - thus no hot water. I cured it by squirting a small amount
of
WD40 at the point where the rod comes out of the flow switch body. You can
get a pair of pliers onto the bar and move it up and down to get the WD40
to
do its stuff. I then cleaned all the gunge off with paper towels, and a
final short squirt of WD40 again. Never had any more problems after that.

HTH
--

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Yep..that's the boiler. I will have a look at what you suggest tomorrow.
Thanks.