Hi,

We have two 11yr old Vaillant boilers (running in series with motorized
valves controlling hot water to upstairs or downstairs or both).

One of the boilers is being a real nuisance. I'll try and explain as much as
I can...

It trips quite a lot, sometimes as soon as you reset it, sometimes it goes a
day without needing to be reset. What will normally happen is the burners
will light up and then you hear a tick tick tick and it fuses. I suspect the
ticking sound is the spark being generated to light the burners.
Another odd thing, when it fuses the light behind the on/off switch comes
on. However, on our other boiler the light behind the switch is on when it
is working and goes off when it trips (only happened once in 11yrs).

We had the Vaillant engineers out about 3 months ago, who said the problem
was that a part was blocked. He had cleared it and said it to be working. To
be fair its been as it is now for a good while now and we're not sure if the
Vaillant engineer did indeed fix it in the first place.

Is there any way to check and see what is causing the fault? I have a
multi-meter and OK with electrics so if its taking readings and comparing to
our other boiler I don't have a problem doing it. I don't want to mess with
the gas though...

Any help/advise would be much appriciated.


David Herman