how can i fix my prima f50 boiler fan not starting?

I switch my heating on but no fan will start up. Ive checked the red wires from the ignition circuit board that run to the fan (0 Volts). If I make the microswitch on the pressure switch the fan starts and the pilot light ignites. Thes system then runs for a while but I would have to re-do it again soon after. is there anything else i should check or should I change the ignition board.