I believe this is what you are looking for!
15 Pole Couplings of Instrument Cluster Up To 07/85
1. Not in use
2. Temperature Transmitter Coolent - Green
3. Sensor Fuel Readout - Blue / Black
4. Sensor Fuel Reserve Readout - Blue / Green
5. Instrument Lights Input Terminal K - Gray / Purple
6. Indicator Light High Beam - White / Blue
7. Indicator Light Ingition Terminal 15 - Blue / Red
8. Instrument Lights Output Terminal 68d - Gray / Blue
9. Indicator Light Ingition Terminal 61 - Blue
10. Indicator Light Brake Lining Wear Indicator - Brown / Red
11. Indicator Light Parking Brake - Brown / Red / White
12. Voltage Supply of Indicators Terminal 15 - Black / Blue
13. Not In Use
14. Not In Use
15. Oil Pressure Transmitter - Brown / Green
Hope This Helps! 