My fan asisted oven is not working on my Zanussi ZHQ575?

Can anybody help. My fan assissted main oven is not working on my Zanussi ZHQ575 built in double oven. The heating elements are working and the fan is working on all other settings but only the fan comes on for the fan assisted oven settting. We think it may be behind the control itself but can;t seem to find a diagram of the control panel works behind the scene. Does anybody have one or know what the problem might be. Thank you for your time.