Fan (heat / ac) not working for the first ten minutes when cold on 1996 BMW 328i

My fan motor takes 10 minutes to start working when cold. The colder the longer it takes to start. Sometimes colder than zero I have to shut it off wait 5 minutes then try it again. Summer it seems to be OK. Final stage replaced, control unit reworked. I did notice I'm not getting power to the final stage when all this is taking place. Question, where does the power come from that feeds the final stage? Can it be as simple as a fuse? Also, when it's not working it looks like it is. Temp settings, fan speed bar display all look OK, but it's not.

Thanks for any direction

Asked by for the 1996 BMW 328i
Is the ambient temperature sensor working? Is the reading corresponding with the real outside temperature?
Is the blower motor still the original?