So, I've replaced the voltage regulator and battery on Lola, and she's running OK. But if I have to go somewhere in the evening, it's a nightmare.

Lights, radio, and heater running at the same time for more than 30 minutes = Dead battery.

I'm old the it's likely the cable, so I bought a new one. I am unable to remove the old one, but I have a friend with tools who can. However, he seems to think the new ground cable should be attached directly to the engine block, and I've read not to do that.

Where should the new ground go? Also, if the old connection location isn't rusty, can I reuse it? Is it safe to connect the ground directly to the engine block? I'm hesitant to put a hole in a big piece of cast iron who's job is to contain a lot of pressure, but I'm a novice, so... please educate me.

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84 300D anthracite grey, tan interior "Lola"

Diesel smells like farvegnugen!

The factory ground cables are fine so long as the connections are clean bare metal. The way the factory has it wired is correct. Grounding directly to the block would also be OK so long as there is a healthy strap from block to chassis but keeping the car as close to factory as possible makes future diagnoses a lot easier. Rather than replacing the ground strap, I would next remove the alternator and have it tested to see if it will produce its rated amperage. You have either a weak alternator or a hidden load such as a stuck-on pre-glow relay.

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970