Originally Posted by Ulfilas
Finally I understood what the electrician meant with "polarizing".
My alternator has an additional field which is initially excited in order to start its electricity production.
He connected tentatively this field (D) to the +B (Batery) through a small 6 Watt 12V bulb.
Once the alternator starts producing energy the volt difference between D and +B dissapears and no more current flows through the bulb.
We suspect a wiring problem cancelling the initial necesary excitation current.
Now the alternator works fine!
I thank the useful advices!.
the excitation voltage is supplied by the battery. A generator will charge with a dead battery but an alternator needs a good battery to charge. So your battery was completely dead? If it wasnt then the battery lead from the bat to the alt has a cold solder joint or some other intermittant open in the circuit.