The Stovebolt Site Forums The Shop Area The Electrical Bay 1948 Chevy 3100 6 to 12 Volts

Is really necessary to install a 125 amp fuse between the Alternator and the Battery when converting from 6 to 12 volt alternator?

I didn't.

Fuses protect wiring, not the battery or the alternator. So which end of the alternator to battery wire do you want to protect?

I guess the real question is on basic 1948 ½ ton , if you have pure bones wiring do you need a 125 amp fuse? Guess that if you add air conditioner and other high amp demand you may need a fuse of that amperage.
The attached photo is from a YouTube channel who did full up restoration.

GM didn't see the need for a fuse between the power connection from the starter to the rest of the electrical system. Of course, they were very cost conscious. The fuse would protect the wire from the starter lug through the ammeter to any fused devices. Of course those wires would let out a lot of their magic smoke before a 125 amp fuse would pop.

Deleted due to incorrect info.

This truck in its past had been converted to 12 volts but I did discover that the alternator exciter wire had been cut off near the alternator and that wire had no in-line diode, also they had incorporated a "idiot light" that was also cut off below the dash. I've installed a new excite wire(with diode) / sense wire harness and wired in the alternator "idiot light." The excite wire is wired to the ignition switch and coil.