Again the Premacy without fan blower

Hello dear people again the Premacy without fan blower Have dismantled half the amature board so that I come to the 4 steps rotary controller. At least there is voltage there. Heating blower starts only when I fill the heater on immediately firing. So at least the fan motor is intact. I turn off the heater also the blower extinguishes. Who can please help me or at least have an idea for troubleshooting. Thank you in advance.