Horstmann 3 channel system problems on one channel

[sharphead]

Hi newbie here,

I've a problem with my heating system, the system consists of a channelplus XL HLH37 with three F222 valves one for upstairs, one downstairs and one for water, the upstairs and downstairs have HRT2 thermostats.
Intermittently when the downstairs channel is switched on the valve is opening but the boiler is not coming on, the other two channels are working fine. Any help would be appreciated

 

[cross thread]

valve not making the end switch to power the boiler,fit a new head

 

[sharphead]

Thanks where can I get a F222m without the valve for good value