Dai
Life time member
Number of posts : 5722
You will need a voltmeter/multimeter or alternatively, a 12 volt bulb in a socket with two flying leads.
Look at the back of the new socket: the red wire is earth (!!!), the yellow wire is dip beam and the blue wire is high beam.
With a voltmeter, on the bike:-
1. Turn the lights on to dip beam
2. Check for voltage on all three wires. Whichever colour has 12 volts on it is the dip beam - connect to the yellow wire on the socket
3. Turn on high beam. Again, check for 12 volts. Whichever colour has 12 volts on it is the high beam - connect to the blue wire on the socket
4. The 'other' wire is earth - connect it to the red wire on the socket.
If you only have a bulb for a tester, do the same as above but earth one side of the bulb to the bike. If the bulb lights, you have 12 volts on that wire.
__________________________________________________
1983 K100 naked upgraded to K100LT spec after spending time as an RS and an RT
1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500