12si upgrade wiring
 

The 10si alt on my 79 has seen better days. Had a new 12si on the shelf. Got it installed and ran a new 6 gauge wire from the the batt post to a 150 mini fuse then straight to the battery. My question is the terminal 1 & 2 on the alt. On my 70 pickup I dont have a gauge so I wired #1 with a diode and #2 straight to the batt post to energize it. With my 79 I have a voltage gauge so unsure the wiring. Can I use the factory wiring and connector for the #1&2 posts with the batt post going straight to the battery?

Re: 12si upgrade wiring
 

Brown wire is the energize wire. Red wire is voltage sense. (not sure which is #1)

OEM wiring has the red wire going to the primary junction block and the brown wire somewhere in the cab depending on idiot light vs gauge. Main charge wire(your #6) also went to the junction block.

Might look for topics on swapping a gauge in for an idiot light. Might be such a thing in the electrical FAQs.

Re: 12si upgrade wiring
 

Caved and just wired #1 with a diode and #2 straight to the batt post to energize it like on my 70. Gauge still works perfect. The factory harness looked like crap so glad to ditch it. Cannot wait to do a new harness

Re: 12si upgrade wiring
 

Here's a link to everything you need to know about 12SI alternator wiring and installation..

http://www.madelectrical.com/index.shtml