There is a diode/relay in the junction box that keeps your headlight off until the engine actually starts. this saves all of your battery juice for the initial start.
However when this diode/relay goes bad sometimes you are left without a headlight totally. There is a way to bypass it but you best make sure you have a maintenance free battery and it's charged because the headlight will come on as soon as the key is turned.
And the relay bypass instructions:
This can be bypassed to operate like an "other than US & Canada" VN750. (European models actually have a switch on the controls to turn the headlight on)
Look at the 8 pin connector going into the junction box. You will see that there are only 7 wires. Move the blue wire to the empty position and your headlight will come on when you turn the key on.
No more diodes, no more relay.
Patriot Guard Rider
2000 VN750 Sere (Serendipity)
1990 GL1500 (Ole Blue)
1986 VN750 EVie (project bike, heavy custom)
VROC # 11628 / 25000-H
ARVROC # 12 Coordinator and Crowd Control
OKVROC # 18 (H)
TNVROC # 45 (H)