Rb25 Charging Dramas

[Yonz]

A couple weeks ago...

The battery in my 31 had been on it's way out for a while, that and I hadn't started it for a couple weeks, so I jump started it and all is well. I leave it idle for a while, then turn the lights and indicators on to check they're all working, when the car dies after a couple minutes of flicking them on.

I put a voltmeter on the battery with car off, it showed 11.4V - dead battery, no surprise there. Jump start it again and it's charging at 13.6V, but as soon as lights are switched on the alternator cuts off and voltage goes to 11.4V and decreases until the battery gives out. I noticed the brake and volt alert lights (top right of the dash) were on as well.

I chatted with a few people and figured switching the lights on was stealing the excitation voltage from the alternator, causing it to stop charging. We figured a new battery would fix it - but it didn't. I put the new battery in and the alternator isn't charging at all now.

I put a spare alternator on which didn't change anything. I also had the old alternator tested by a mate that's got all the gear and it's working fine.

I replaced all the fusable links and had a breif look over the loom, and noticed this rather confusing event.

Also got the voltmeter on the alternator plug.

Alternator plug: small white and black wire 0.5V
larger white and blue wire 11.5V
Are those meant to be about that?

All I can think of is a bad earth or perhaps a sticky relay?

Anyone had this issue before?

[Yonz]

Found the issue, a couple wires in the body loom had rubbed through and were slightly contacting each other