Hey all,
I recently swapped in an LS engine using the ACE kit and would like to install some gauges to monitor it's performance just in case something goes awry in the early days.
Recently I purchased the Innovate Performance combo oil pressure/temp gauge and plan on getting the water temp/battery charge gauge in the future.
I'm planning out the wiring and wanted to get some advice on my direction so far...
It looks like the S12 connector in the fuse box under the steering wheel has an empty plug labelled S12. I found a bunch of info on it from this thread but here's the main info.
The gauges will need the following wired up:

1. Switched 12v - which terminal 5 and 3 could provide to each gauge. They need a minimum fuse size of 2A.
2. Ground - Hoping I can connect the grounds from each gauge to terminal 1
3. Headlight power wire (supplies power when the headlights are on) - this should not be spliced into the dimming wire. Not sure if terminal 2 would work here. Need to check to see if this gets power only when lights turn on.

Looks like I can order one of these connectors from eBay: https://www.ebay.com/itm/161745162895
Thanks for your help!

The terminals in S12 are numbered from the bottom upwards -

viewed from the rear (cable entry side) of the connector

The circuits are as follows -

Terminal-5 - Live - ignition switched (position 1 on ignition switch), via F27 (10 Amps)

Terminal-4 - Live - permanent, via F20 (15 Amps)

Terminal-3 - Live - switched, from auxiliary circuits relay, via F15 (20 Amps)

Terminal-2 - Live - from main lighting switch (sidelights position), via F33 (10 Amps)

Terminal-1 - Earth - via C0583 to C0017-1 (Earth Header) on 3.0mm² cable

 

If you make it to a yard, that is also the windshield wiper motor plug. I did a bunch of research and found this a few years ago. I used it to wire an oil pressure gauge.