I dont really follow your explanation but if you replaced block with new fuse block and same side of block fried as did the last one, then i'd replace the entire wire run from that side to wherever it goes and make sure wherever it's attaching to is free of resistance and corrosion.
I guess the other side could cause the issue too if you want to replace the whole nine yards.
I would replace the block again, measure ohms from batt to other side of fuse block with car off.
Then measure ohms from the fan to the side closest to batt on fuse block.
If they both measure 0.0ohms, then start the car and let fan come on. Wait ~2minutes then remeasure but measure dc VOLTAGE this time at the batteries posts then measure voltage at the fuse block before and after the fuse and at the fan and use ground on batt as ground for all readings.
Once you see a dip in voltage, you know everything behind it is in question.