at what speed does the electric fan stops been "usefull"??

i made a switch for it since the relay wasnt the problem and it wasnt turning on for some reason...but i want to know if having it on all the time is as effective when going over w.e speed...

 

It's probably not doing much at speeds over 45mph, but just watch your temp gauge (assuming you have one, and not just a dummy light). Maybe lower, my temp never gets over 210 unless I'm in stop and go traffic or just sitting and idling, and the e-fan doesn't kick on until it hits around 220 IIRC.