1) You don't happen to have a wall mounted thermostat anywhere?
> I've just replaced the timing unit for my Vaillant combi boiler as its
> never worked properly since I moved in. What I expected to happen is
> that when the timer is set to ON, the heating/hot water will come on
> (providing its selected on the boiler itself), when the timer is set
> to OFF, only the hot water will be available.
> Unfortunately, this isn't the case. It looks like the zone valve isn't
> working in the boiler. (I've checked and made sure that the timer
> works correctly).I do know that when the Vaillant engineer came to
> look at it prior to me moving in, he couldn't get the timer working
> and therefore "wired it direct" whatever that means.
> I assumed that this meant he'd bypassed the timer although now I
> suspect he also bypassed this within the boiler.
>
> Does anyone know how I get round this? Is it safe for me to go delving
> around inside the boiler itself?
>
2) All vaillants require a connection between terminals 3 and 4 to run the heating. This applies to Sines, VCWs, & Turbomaxs.
It's mains powered electrical appliance no more dangerous (less actually) to delve into (electrically) than a toaster.