Yes, there are three wires on the starter, not including the battery cable.
One goes to terminal 50, one goes to terminal 30 (battery cable) and the other goes to terminal 16.
The wire to terminal 30 (battery cable) powers all the accessories and ignition switch -- if the radio doesn't work, this is probably the wire that is off, and the starter won't work since there is no voltage being applied to the solenoid when you turn the key. Probably red, but not marked on my diagram.
Terminal 16 goes to the ignition and bypasses the resistor to give hotter spark when cranking.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!