...for my '89 4runner V6. I searched and searched and looked at lots of threads but couldn't find good info about upgrading the charge wiring. I have the wiring diagrams from the FSM but I'm still not sure whether to run a replacement/upgraded wire from the alternator to the main fuse block on the right inner fender or directly to the battery.

The alternator I'm putting in is a 100 amp unit out of a '91 MR2 turbo.

 

I did some investigation on some actual OE parts in the mean time. I have an '89 4runner parts truck that I just pulled the #2 relay/fuse box and the alternator wiring harness off of. I think the main charge wire is 8 gauge and a straight shot to the main fuse and then on to the battery.

I'm gonna do an autopsy on the old harness later today to confirm that the main wire runs direct from the alternator to the main fuse.

I also found out that I can get a 120 amp fuse that is a direct replacement for the original 80 amp. Only $3.40 at at the local independent parts house. Now my only worry is that the fuse holder/fixture is beefy enough.

 

A picture of the alternator charge harness and the #2 fuse/relay block.






And one of the troublesome (hard to remove the first time) main fuse holder and the fuse itself.