My buddy's RPU has an electric fan that quit working. I looked at the fuse box and the fuse had fallen out. It has a 30A relay so does it use a 30A fuse?
A 30 amp relay is only a switch whose contacts can withstand a 30amp load. Installing a 30 amp fuse for a circuit who's wiring may only be rated for 10 amps will melt the wiring before the fuse pops.
Check and see what wire gauge is going to the fan from the relay and fuse with the correct rating.