[trularin]

You have too much resistance between the alternator output and the battery. There is some kind of problem int he cable or your connection.

May I suggest you trace the output of the alternator back to the battery and see where it drops from 22 Volts to 12 Volts.

The difference is usually no more than 3 Volts from the front of the car to the rear. If there is, it is due to either too small of a wire used or a bad connection.

Just my opinion.