78 300D alternator question
 

My dad Had problems over the weekend in his 78 300D, he just had all the seals replaced on the transmission since it was leaking badly. All seemed well until the battery light came on and the radio turned off.

My dad thinks the alternator is dead as the battery wont hold its charge, he was stumped on one thing though. He jump started the car and disconnected the battery, he said if the alternator was dead the car shouldnt be running and it was.

My guess and its just my guess as im limited knowledge of gassers, my guess is that the car still runs do to the fact that maybe he is thinking of a gasser. I would assume a gasser needs power from the alternator to get the spark plugs to spark right? And therefore the gasser wouldnt run but the diesel will since its based only on compression with no help of spark plugs.

Well i had tried out a couple of things while the battery was disconnected, it seemed that the lights didnt work interior and exterior. The radio didnt power on either. I assume its the alternator thats dead and the diesels compression only is whats letting it run without the alternator.

Am i correct in my assumptions? any other suggestions, im going to pick up an alternator from my work and give it a try to see if it is indeed the alternator.

MB diesels up to 1996 needed only liquids (fuel, oil, & water) to stay running...

As you have seen the battery is needed only to start the engine.