Ravenheat csi85 no ch

[sulliwag99]

I have a Ravenheat csi85.The hot water works fine but when I turn the central heating on it goes off after about 60 seconds.Can anyone ease give me some advice as to what it could be

 

[Aquarius]

Can anyone ease give me some advice as to what it could be

Diverter valve or microswitch not connecting. Probably best getting a suitably qualified engineer (gas safe in uk).