87 300D electrical charging issue found.

[vstech]

OK, the car got a 90 E300 alternator upgrade, and I STILL could not get the car to charge the battery...

tested the alternator, good.
car started fine, but would NOT maintain charging.
I'd start the car, I'd get 14.1 volts, then it would slowly drop down to 12.2... TOTALLY miffed me.

I didn't think it could be the ground strap because the car started fine.
I was wrong.
the ground strap was loose, and pitted. I took everything apart, cleaned and filed smooth the strap, and the bolt, and went to tighten everything back down only to find that the threads are gone in the bellhousing... CRAP! the bolt would not pull tight. (is the bolt supposed to poke through the motor plate? I think it's the wrong bolt.)
anyway, I drove to the parts store, and picked up a 40" ground strap, and removed the ground cable from the body connection at the battery, and cleaned it all down to the metal, and put the new strap in there, then routed it through the bushing in the heatshield, and routed it over to the intake manifold. I put it under a shield bolt to the manifold.
INSTANT starter action, and the alternator now puts out 14.3volts with EVERYTHING on.
I bet this will fix the temp gauge problem I had too...