My Vaillant ( think it's a turbo as has black panel with green knobs as described by others ) is ten years old and hot water has recently been playing around ; problem is having turn hot tap on and off to get boiler to fire up for hot water ( heating on or off not an issue - yet ) but just recently we've had to turn boiler off then on on the green dial on black panel to make hot water work, then next time water just fires up like it should.
I'm a builder , so spoke to blokes I know at Plumbcentre and they said try replacing the diaphragm, so I bought one for the princely sum of £5:90; prob is I.ve lost instruction manual so can't see where and how to exchange part.
Help ?
Am I wasting my time ?
Is it likely to be diverter valve.
Any advice appreciated

Keith Reed, January 2010

Hi just recently had problem with old boiler had hot water and no heating. Heating not getting hot enough. Turned out the divertor needed cleaning out as boiler gives priority to water and not heating the element wasn't connecting to switch over to heating and so not firing up. But I was told by the engineer all boilers should have their manual with them part of the new gas safe rules. Just phone up vaillant and ask for your maintenance manual and they will send it out to you.

wendy, January 2010

get a manual

IPS boilers, January 2010

if was the diaphragm , switching the boiler on and off would make no difference. I think your problem lies elsewhere, most likely an electrical fault.

Henry, January 2010