SIME super four : no heating

[shmelv]

can one of you guys give some advice on the following boiler which has a problem :

its a sime super four as above, hot water is fine ( very hot if this means anything) ! but when switching the heating on it sounds as if the pump is running and fan but there is no heat going to the radiators. the circulating pump (right hand side) has been changed a couple of months ago so that i assume is ok .
(im not 100% sure but it seems as though the boiler may fire briefly but not pump water to radiators)

look forward to you guys expert help ! cheers

 

[bobw1956]

Check the diverter valve

 

[shmelv]

thanks for the answer but i believe these boilers do not have a diverter valve but instead have two pumps.