built in fan assisted oven won`t heat?

my fan assisted built in oven won`t heat although the grill element in the oven works fine and thermostat light is on.Could it be the the fan element but the fan works but no heat.If it is how can I prove so and could it be fixed D.I.Y. or would I need professional help.It`s an electrolux model#eob5600.Any assistance gratefully appreciated as I am dying for some home cooked roast beef.
Podger