hot water but no central heating

[wilkodrive]

hiya folks
i am able to call for hot water via the programmer no problem,ie the boiler clicks and lights.When i call for heating,no clicking to light the boiler.I have had the reverse problem in the past and replaced the programmer which solved the problem,However,having tried 3 new programmers just to make sure they weren't faulty,this obv hasn't solved it.Two of the programmers were like for like and i tried a different make for the third,same wiring etc.It is as if the boiler isn't recieving the signal for the heating???Don't know if its linked but the rads upstairs come on boiling hot with the water.Any advice would be appreciated,very pregnant wife moaning about the cold!!!

[DEEARR2]

Without knowing how the system is piped there are a few possibilities. the problem with 'no heating' may be caused by a faulty motorised valve. This valve wold be controled via the programmer and possibly a room stat. When the motoised valve for the heating is signalled to open it actuates a micro switch which in turn would signal the boiler to fire.
Upstair rads heating while on HW only could be caused by back feed through the return pipework. Indication of this would mean the return pipe on the upstair rads heats up first.

[rosebery]

It could be a faulty 3 port valve or a faulty roomstat or or......

I think you need a visit from your friendly neighbourhood heating engineer TBH.

Cheers