On 23 Jan 2007 14:29:41 -0800, "drb" wrote:

We have a 22yr old Vaillant VCW Gas open flued boiler, doing CH & HW

We've recently had it serviced, including having the heat exchanger
fins removed & washed clean of debris. A new thermocoupler was
installed too. It then worked fine for approx 3 weeks.

The Sine VCW has a simple pilot light and thermocouple set up. If the
pilot light isnt staying lit then its either the pilot burner thats
defective in some way i,e partially blocked,or the t/couple. There is
an interlink inside the control box but all this does is operate a
microswitch when the pilot has been successfully established,so
providing power to the next control stage. I have some of my own notes
for the VCW including functional flow diagrans, If you send me an
email I'll pdf them for you..

email to but dont forget to change the 1999
to 2007 before you click send!