Sterling Power Products PDARRC manual Volts Neg B

2 x wires fitted		Positive field control alt
by the installer as		( most common in American alts )
per the fitting instructions
and brought outside			2-12 volts
the alternator case		0 volts		s
0 volts	14 volts	0 volts		14 volts
		neg		A
0 volts	14 volts
neg

carbon

brushes

B+

main positive output

B+

main positive output

Diagram 4

Diagram 3

Confirming negative or positive field control Diagram 3

Because the regulator is usually built into the back of the alternator, there is no way of knowing if it is a neg or a positive field control alternator from the outside. However if we were to fit a wire on each brush and bring them outside the alternator case, then we can check the voltage at the brushes, and make some deductions. In the above case there is no regulator, so one brush will be 14 volts and the other brush will be 0. In real life this would never happen,

Confirming negative or positive field control Diagram 3

Because the regulator is usually built into the back of the alternator, there is no way of knowing if it is a neg or a positive field control alternator from the outside. However if we were to fit a wire on each brush and bring them outside the alternator case, then we can check the voltage at the brushes, and make some deductions. In the above case there is no regulator, so one brush will be 14 volts and the other brush will be 0. In real life this would never happen,

Negative field control alt

( most common in europe )

s 14 volts

0 volts

14 volts

neg B

B+

main positive output

Diagram 5