3.8 tarus fan install electrical issue

[5150coupe]

i installed a ford taurus fan into my 89 5.0 and i'm having trouble with wiring. i melted the 75 amp relay/fan controller and so i went directly from the fan to a 40 amp fuse to a 50 amp toggle switch to the battery, so it was manually controlled. the 50 amp toggle switch melted. the only other wiring is a diode between the positive and negative to protect the fan motor. it always felt hot around the switch like there is resistence, but there shouldn't be with a 50 amp toggle switch. i'm running the fan on the high setting. with the fan running it only felt hot around the toggle switch. can anyone explain why the 50 amp toggle would melt before the 40 amp fuse and why the fan would melt anything that high in amperage?

note: i also upgraded to a 150 amp alternator to support the fan and future electric water pump.