Hi Guys. I recently acquired my first MB!!! It's a 1984 MB 190E 2.3 L. This is an awesome car. I can't wait to "fix it up" with some classy upgrades etc...

Before I do all that, I want to get it running really well (it's actually in very good shape with only 104,000 miles).

I'm having an issue with the Batt, alt or Volt Reg at the moment and I'm wondering if any of you have ever had this problem.

At night (only-so far), the battery looses it's charge completely to the point where it won't start. I replaced the battery and it still does it. Once I start the car (boost) it will run fine for hours... I tried the old alt test and ran the car with the batt negative pulled off, it runs fine.

Very strange... I'm assuming it's a cell in the alt or the volt reg or a loose belt??

Any input would be awesome, I plan on fixing it tonight.

Thanks in advance.

Sounds like you have an AMP draw. Something is staying powered up when the ignition is turned off.
You can check this with a digital multi-meter.
You would what to set the meter to "amps" and unhook the negative cable
Hook one lead to the cable and the other to the negative battery post.
You should only have 0.03 amps or less.
If you have more, start pulling fuse to see what is causeing the power draw.

check your wiring where the battery is

Never perform the "old alt test", as this will damage the charging system.

+1

Alts do not have cells, batteries do.