I have had a charging problem for several weeks now on my 89 240 and I'm trying to solve it. I have a new alternator, new battery, and my new battery was dying daily. I recently replaced the battery cables and is not dying daily but the voltage at the alt seems to be low as well as the battery while idling. I say it is not dying daily, however 2 days ago, the battery was completely dead and left me stranded in a store parking lot. The battery read 0 volts. Today it has not died, and I drove it several times. I am getting 12.56 volts at the alternator at 600 RPM (my idle speed at park). If I turn lights on or AC with fan it dips below 12 volts. If I turn those accessories off, the battery climbs to 12.56 volts at the battery. Shouldn't I have over 14 volts while the car is running?

I have a real mystery on my hands and I'm completely sick of this dying battery issue and poor charging. I am going to change the ground wire on the alternator as it looks old. Any ideas and info?