Many thanks Dave. I had a similar lack of hot water and fiddling with the Diverter Valve has fixed the problem. Not sure if it was a loose electrical connection or jammed valve (I think the central screw/connection rod was improperly connected).
To fix (Vaillant Turbomax Plus):
Open front panel. Open electrical panel by turning the plastic screws (top left, top right of display panel) and pulling the panel (it hinges down like the normal cover plate). Switch off mains power.
The Diverter valve is to the bottom left. Mine had a black unit at the top with three wires going to the front panel. This was held on with a metal screw fix pipe join. A was able to unscrew this by hand (and the central internal connection rod dropped out - quick hunt around the floor). Don't worry - no water.
There is a central pin inside the valve. Pushed in, it allows hot water. Pulled out it does central heating. I manually pushed and pulled this central pin to ensure free movement (reasonably stiff).
[warning - the following should be done with extreme care]
To replace the central connecting rod (remember it dropped out earlier) I switched on the mains power and opened a hot water tap - this should cause the Diverter Valve Actuator to extend (push) (if it doesn't vibrate/make a sound it or the electronics need replacing). I then turned off the power (and the hot water). I then inserted the screw end of the connecting rod into the black head unit and screwed it in as far as possible (only a few turns). Holding the entire head unit I then hooked the other end of the connecting rod onto the central pin of the Valve (this was easier than I estimated). I had to push the valve in (I had set the head unit to extended (hot water) earlier) to screw on the pipe fitting (hand tight only).
Close up and all done. Lovely hot water. And a bath that doesn't leave me blue and shivering.
Mark, April 2005
