Howdy fellas,
You guys will know this stuff in your sleep, but I'm the diesel newbie and I just gotta know: how exactly does the battery idiot light work in the 123? My charging system took a crap last week (stranding me roadside twice!) so I swapped the voltage regulator. BUZZZZ wrong answer. I've got an alternator on order now.
As I understand it, the charging system is like any motor - alternator spins, internally rectified to DC, regulator regulates by reading battery voltage, wiring goes from alternator to battery + (stopping at solenoid along the way). Yes, I checked for continuity from alternator to battery. Yes, the battery is new and takes a trickle charge on the charger like it should.
My question is if the car wasn't charging, why didn't the light come on? The light itself works when I crank the car. How does this light "know" to come on at low voltages?
Last question: my method of testing the charging system is to turn the wipers on and disconnect the battery with the engine running. I know not to do this on a gasser (possible surge blows out ignition system). Is there any reason why I shouldn't be doing this on the Benz?

Thanks,
Kip Amore
77 240d