Hello there,
I decide to add a transmission cooler to my el v8, with a 10" fan on it. I am a little bit confused about the wiring.
The cooler also comes with a thermo switch, so my plan is get a power sourse from ignition switch, so that i can turn off the fan when stop the engine, thats not flat my battery. And then have a relay , and the switch, and the fan at last. Ignition-relay-thermo switch-fan
But i am not sure if the switch can survive from the current, i am told i must put a 30A fuse when i am wiring. If the switch is blown,game over.

An other plan is ignition-thermo switch-relay-fan.

which one is better and safer?

i honestly wouldnt bother, if you run the trans cooler by itself(not through radiator) and its mounted close to the radiator/condensor, the engine fans will draw enough air to cool efficiently enough to not require a added fan..
keep in mind running your trans to cool can be just as bad as running it to hot..