hi,im andres, i used to have the same problem,look, please make shure all the wires are pluged, and all that stuff....but...first turn your amp on without speakers...then give the amp some volume a half or full,i your fan dont turn on,the only thing you have to do,its clean up the fan,make shure is working properly,why??because is an overload protection,when the volume is raised up,the fan will run,if the fan doesnt,the amp will protect and display "overload"....im shure it will work.
i hope this is usefull.
andres