Hey gang, I've got a 79 300TD with a starting problem.

Here's the scenario:
- brand new MB battery
- get in the car and the dome light is on
- turn the key and get the usual dash lights for a hot sec and then gone in the blink of an eye
- no crank no nothing and then there's no power anywhere - even the dome light and the second try there are no dash lights at all
- check the battery and it's at 12.9 volts after all of this
- same effect when jumping the car

- if I charge the battery then it all starts over again with the dome light and brief dash lights

Any thoughts? Ground issue? Just need some ideas where to even begin to start troubleshooting this.

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