radiator fan should be automatic. also thermostat valve should be installed.
pros:less load on electricial system, longer fan life, better economy and power, longer engine life.
in case of heating problems, old and bad quality water hoses, very old radiator, wiring issues etc use dirfect fan till problems are fixed.
if you need detailed info search for these on forum. A lot has been said on these topics by senior members and it has been explained in detail.