Vailliant Combi Boiler bugging me

[Andygasman2010]

The hot water servo is dead centre, to the right of the PCB housing and to the left of the gauges. If you have a close look while someone turns the hot tap on and off you should see it moving up and down. You need to make sure it drops fully down to it's rest position. Get the boiler into it's fault state and push down on the servo arm. If it fires up as you do this you'll need a servo and/or a water section. Or maybe you can strip/clean/repair.

The diverter valve is on the RH side. It's controlled by the hot water servo so do the above test first.

 

[MrV]

and i take it the mains terminal strip is under the metal cover on the right hand side of the boiler.. theres a metal one with 4 flat blade screws and a black plastic cover underneath with 1 flat blade screw in the middle. Which one should i remove?

You mean the left side??
The plastic cover is the electrics cover, but only do this if you're confident with electrics. No offence.

 

[Andygasman2010]

and i take it the mains terminal strip is under the metal cover on the right hand side of the boiler.. theres a metal one with 4 flat blade screws and a black plastic cover underneath with 1 flat blade screw in the middle. Which one should i remove?

You only need to remove the black plastic cover with one screw, it's on the LH side isn't it??

Do the servo tests first, and look at the diverter valve, as MrV said! It's an easier test.

 

[Dougie212]

located the diverter valve... are the micro switches viewable from the side through the clear plastic part? I cant see them at present.. its rather a squeeze in our cabinet

 

[Andygasman2010]

The clear plastic cover comes off for closer inspection.

It's easier to see the DHW servo arm... have you done that check?

 

[Dougie212]

no... wheres that and what do i do please?

 

[Dougie212]

found it... just need to know how to test please

 

[Andygasman2010]

The hot water servo is dead centre, to the right of the PCB housing and to the left of the gauges. If you have a close look while someone turns the hot tap on and off you should see it moving up and down. You need to make sure it drops fully down to it's rest position. Get the boiler into it's fault state and push down on the servo arm. If it fires up as you do this you'll need a servo and/or a water section. Or maybe you can strip/clean/repair

 

[MrV]

You've been given two tests to carry out.
Get them done and feed back your findings first so we know what is working correctly..

 

[Dougie212]

ok... quite oddly.... having found the servo and about to look i have turned on the CH and everything kicks up but the burners dont fire.. they did 20 minutes ago and arent now.... uh..!!??

help...

 

[Andygasman2010]

Carry on with the servo test, push it down and make sure it's fully home. See if the heating comes on.

 

[Dougie212]

done that and no.... it fires when i turn the hot water on and i can hear the relay clicking which usually signifies its going to light but it doesnt

 

[Andygasman2010]

Now take a look at the diverter valve and watch it's movement. It should be fully outwards when on hot water, in the middle when at rest, and pull fully inwards when the heating is on.

Make sure the diverter valve is fully inwards and is making both micro switches.

 

[Dougie212]

the diverter valve is doing exactly as you say.... again... boiler is running now but no ignition of the burners when I put CH on.. it was earlier today.. is it possible its all the on and off ive been doing has caused it?

 

[MrV]

Does it fire up immediatley when you open the hot tap?
What is the temperature control knob set to?
What is the room stat set to?
Behind the black plastic electric cover plate is a "Jumper" with a wire link on it. it should bridge a common pin to a number. What number is it on?