In an earlier contribution to this discussion,
TallJim wrote:

Thanks a lot Tony, that make lots of sence. I think it is a S-Plan
boiler (Vailant 112E), and it does has 2 MV's. I will try to follow
through the circuit to see it I can find the problem. I assume if the
MV's are both still working, then the most likely problem is the
programmer ? Although I can't believe so many things went wrong at
once.

If it's an S-Plan system, have a look at the S-Plan diagram in
http://content.honeywell.com/uk/homes/systems.htm

You will see that the CH MV is fed from the programmer via the room stat.
Similarly, the HW MV is fed from the programmer via the cylinder stat. Both
valves have a pair of 'volt-free' contacts (i.e. electrically isolated from
the motor feed). When a valve opens fully, these contacts close. One side of
each pair of volt-free contacts is connected to permanent live. The other
side is connected to the boiler and pump (or just the boiler, if the boiler
controls the pump to provide pump over-run). So, when either or both
circuits are demanding heat, the appropriate valve(s) should open and - in
turn - switch on the boiler and pump.

So you need to trace the wiring for each circuit - from the programmer,
through the stat to the motor - to see what is live when it should be, and
what is not.
--
Cheers,
Set Square
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