Vaillant VCW-sine 18 T3WFH - main burner not coming on fully

[Chevy82]

Problems with my trusty old Vaillant.

When the central heating or hot water tap are turned on, the main burners will ignite as normal. After a second they used to come on even stronger, but this no longer happens.

Result is warm, but not hot tap water; and central heating that take slightly longer to heat the house.

Additional things that may be worth saying
- I have to pump up the expansion vessel every 3 or 4 months.
- took the diversion valve apart and gave it a good clean 6 months ago. (The rads used to come on with the hot taps, but this is now fixed)

Any ideas?
Cheers

 

[Agile]

Unfortunately the forum rules dont permit us to give advice on gas/combustion related matters.

You will need a gas reg engineer who is conversant with your model and ideally electronics as well.

Tony

 

[Chevy82]

I was hoping there was something I could try with switches/sensors/valves on the water side? It seems like there's a switch not making, Possibly due to water temperature?

 

[Agile]

Its easy to hope! But the reality is that the fault you have needs to be fixed!

I always hope that I will do the lottery. But the reality is that I dont !

 

[Chevy82]

I was hoping for help, but in reality all I got was a riddle.

Not to worry, I figured it out in the end. It wasn't gas related.

 

[Bunnyman]

What was it then ? Stuck pd valve?