Lima Failure: Tachometer Works, Oil Light Flashing

...and all of this happened suddenly, all at once, starting yesterday.

Hello everyone, my name is Stephan and I'm from Berlin. I mostly work on American cars (Camaro Crossfire, K30 Army Pickup with a 6.2L engine).
As my daily driver, I have a '93 III TD (it's actually missing only the 'I' ).
Does anyone know what happened to me yesterday?
I was told that it probably completely destroyed the entire dashboard unit, but I don't understand how that could happen if the battery no longer charges.
Okay, so basically everything is working on the instrument panel, except for the tachometer. The battery warning light is dim (almost goes out when accelerating), and the oil pressure light is constantly blinking. I think the oil pressure is actually fine, and there's just an 'electrical problem' somewhere that's causing the light to behave that way.

Can anyone tell me exactly where the cable from the alternator (D+) goes? (To the relay? To the ignition switch?)
Today, my car broke down due to a power shortage. I then connected the D+ cable directly to the positive terminal of the battery, and now it seems to be charging again.

Sorry everyone for all the questions, especially since this is the first time. But that's how things usually start.
'That's a really clean board, by the way!'

D+ goes from the ignition switch to the instrument cluster and then to the alternator. Your charging indicator light essentially acts as a current limiter for the excitation circuit. So, if something has burned out in your instrument cluster, it's possible that the alternator is no longer being excited, and therefore is no longer charging.