Aftermarket fans are too much load on the stock electrical systems. You need everything upgraded
EDIT: I also have a high output (140 amp) alternator that is standard with the CVF Wraptor serpentine belt and accessories system.
As voltage drops below what an item requires to function, current will rise generating heat. That's one reason why I checked for voltage drops, but all points were w/in range.
I have all new, dedicated wiring, control modules, and
relays for the electric fans, Dakota Digital RTX dash, and a couple of other things.
My problem(s) on the Roadrunner was having the electric TWO SPEED motor on a single 18" electric fan and shroud assembly, over 4 star rating online, and "the only brand I carry because I haven't had ANY problems from my customers" is what my vendor who sells all kinds of hot rod and aftermarket products and accessories and should know...Despite all of those assurances, I burned up THREE electric motors and I gave up. I installed the compact blade style flex fan, and TWO SPAL brand pusher fans, connected those 2 fans to the SAME relays and control modules I had the single 2 speed fan hooked to, and they have been FLAWLESS in their operation.
I have an electrical/mechanical background, discussed my situation with the fan manufacturer and he is knowledgeable, checked multiple points for voltage drops, and STILL had the 3 fan motors burn up.
I saw SPAL on 95% of the cars at a show, and it's probably the ONLY brand of electric fan I'll ever use now.