no heating only

[adapt]

i cannot get heating only to come on. the boiler will not light but when i put hot water on boiler comes on fine, room stat is ok 3 way valve is ok .
I have to have the programmer on for water and heating for the heating to come on, Any body got any ideas....

 

[D_Hailsham]

3 way valve is ok .

How do you know? What tests have you done on the valve?

 

[twgas]

If what you say is true then I would suspect there is no HW off connected from programmer to valve.

 

[MANDATE]

unfortunately the 3 way valve is not ok.
It might go to the correct position, but a faulty micro switch within the valves head would prevent the boiler from lighting.
This switch is not used for this purpose whenever HW is included in the demand (power from cylinder stat lights boiler)
If valve does not go to correct position, then that could be due to, wiring fault or valve spindle too stiff or valve motor/ micro switches.

 

[adapt]

i have replaced the 3way valve and the room thermo...

 

[D_Hailsham]

Do you have a multimeter? If so check that there is 230V between the valve's blue and grey wires when CH only is required. You need to check this under two conditions:

1. HW is ON at timer and HW stat turned low.
2. HW is OFF at timer.

 

[twgas]

If what you say is true then I would suspect there is no HW off connected from programmer to valve.

still looking likely

 

[D_Hailsham]

If what you say is true then I would suspect there is no HW off connected from programmer to valve.

still looking likely

I agree - it's just a case of persuading the OP to carry out some tests to confirm this.