icos he15, no heating

[tj49]

hi, we have a problem with are heating, when it is switched on nothing happens, we have a Honeywell st9400c programmer and just set to to continuously when we want heating on, the light comes on but nothing is happing at the boiler, we can switch it to heat water and the boiler fires up straight away, its been getting worse over the last week to a point now where it was left switched on all day and night and heating never came on at all, just wondered if this might be a faulty programmer as the heating side switch is harder to press than the water side, thanks

 

[Harvest Fields]

If the light comes on at the timer and the thermostat is turned up. The first thing I would look at is the motorised 2 or 3 port valve (dependant on system set up) in the airing cupboard.

 

[townfanjon]

As above ^^^ what are the manufacturers valves in the cylinder cupboard ?