Intermittent HW problem with boiler.

[emc11]

I am having an ongoing intermittent issue with my Vaillant Turbomax combi boiler.

At first I wasn't getting any hot water unless the central heating was on. This seemed like a standard problem with the diverter valve. A repair guy came out and thought the same a replaced the valve. However this did not resolve the issue although it did seem to make the problem a lot less frequent.

The main symptom is basically as follows:

If the HW has been running for a long time, when the HW tap is turned off, the next time the HW tap is tuned on the boiler does not fire up. This does not happen 100% of the time, but it does appear to be a consistent pattern. When CH is on the HW is always fine. Turning the boiler for for 5 mins usually fixes the problem, although I think it resolves itself after some time anyway.

Does anyone had any idea what the problem might be. It is driving us crazy, and the repair man say he cannot diagnose the problem.

Thanks

 

[RusClarke10]

This fault would suggest that the micro switch on the diverter valve is out of adjustment

 

[emc11]

Thanks for the reply! Would this problem occur even with a new diverter valve?

 

[Rob]

Ok firstly there are two types of turbomax. The older type with black facia and green knobs and the new type with white facia white knobs and usually has a digital display.

 

[emc11]

Its the older type with black facia and green knobs.

 

[Agile]

I dont really understand how a boiler engineer cannot have any clue whats wrong with your boiler.

Or perhaps he has changed the diverter valve, charged you about £180 and made his money and left you with a boiler which is still not working?

Tony