hot water but no heating

[adapt]

i can get hot water and heating. or hot water only but not heating only. The 3 way valve is new the pumb works ok. if i turn on the programmer for heating only the boiler will not light. if i ask for ch and water it lights ok.
Anybody got any ideas.........

 

[gaspro1981]

possible componant failure but could just be a wiring fault

 

[busker]

I had a similar problem and never really identified why for sure. However, it seemed that several manual over-rides (advance, 1 hr, on, off etc)upset the programmer. Turning off the power to the system for a while, switching back on and re-programming got things back under control.