OP, I had the exact problem, just got around to it today.
My reserve lighting devise (RLD) failed to test ok, and I wired around it for now. Headlight works as it is supposed to now. For now I have a 'two wire twist' otherwise known as a panhead ignition switch. I did not disturb the original wiring harness.
Using this forum, I will try to determine the amount of issues that occur with the RLD. If they cause little trouble, I intend to R&R mine. If the consensus is they are problematic, I shall permanently wire around mine.
By your description, I suggest the following:
Remove the right side cover. You are now looking at the RLD. If in doubt, it says so on it.
Turn the ign switch on and bump the starter, the headlight should come on.
Once the headlight is on, unplug the RLD. You now have the devise side plug and the harness side of the plug. Test the voltage on the BL (blue) wire harness side. should be bat voltage or close. Mine was 11.85 volts.
If you have sufficient voltage, turn the ign switch off and perform the tests on the devise side connector.
Set meter to ohms, BL, BL/Y, BL/O to BK/Y must be open.
BL to BL/Y must have continuity.
BL to BL/O must have continuity. This should be your problem.
there are other tests to perform, mine failed the last.
Last edited by wmsonta; 05-19-2013 at 04:26 PM.