I have a Vaillant Turbomax 828E Combi boiler which is about three years
old now and have just started having problems with it and need some
advice!

When the boiler is set to run with the warm start on, the heating fails
to switch off even though it is on a TimeSwitch 100 timer. The only way
to prevent this from happening and for the heating system to run
"normally" and to the pre-set times is to turn the Warm Start off.

However, I have found that when the warm start is off, obtaining hot
water from the boiler at times when the heating is off (i.e. during the
day) is near impossible and I have to either reset the boiler or turn
on the warmstart. Getting hot water when the heating is on (i.e. first
thing in the morning and evening) is fine with the warm start off.

I hope this makes sense and someone is able to help me out with this
problem. To summerise the main problem is:

When the warm start function is enabled, the heating system fails to
switch off in line with the timer and is effectively running all the
time. This does not happen when warm start is switched off.

Thanks to all in advance.

Ben