location ammeter main terminal S2

Except 12V+ on the terminal post and the startermotor I have no voltage anywhere on this P6B S2 from 1972, out of service for about 40 years....... The two brown wires from the terminal post connect to the alternator and ammeter main terminal incl ammeter shunt, number 3 in the electric cicuit scheme. That terminal is my next 12V cheque aim. But where is that terminal located ? In the mean time cleaning all under-dashboard and -bonnet electric contacts.