Toyota Repair: corolla RDI fuse, jumper wire, fuse box

Question
I have a corolla 2000, everything seems fine, no warning, checked the main fuse box and the one designated as RDI 30A was blown, replaced again blown, no warning light etc.
My question is that how can I figure out the diagnose problem (unseen) problem with this fuse, as there is no warning. ( I guess the fuse is for fan#1). Many thanks  

Answer
Try disconnecting the cooling fan and see if the fuse stays intact, the fan may be drawing too much current which means the fan motor may be shorted internally, apply 12 volts across the terminals at the connector to the fan and see if it spins, use a jumper wire with an inline 30A fuse, if the fan is shorted the wires will burn without the fuse in it. If the inline stays intact with the fan motor turning, the fan is not the problem. If the 30A RDI fuse blows even with the fan disconnected the problem lies elsewhwere, let me now.