I discovered this is a common fault in BF falcons - the headlights stop working, and it seems to be related to the indicator stalk.
Quite some time ago the "Auto" headlight setting on the falcon stopped working. I wasn't too fussed about that, I'm pretty capable of deciding if I need the headlights on or not. But when I'm driving at night, and each time I put the indicators all the lights are turning off, it's time to investigate.
Well, good news, it's a reasonably simple task to fix if like me, some wires from the headlight switch have snapped. The indicator stalk mechanically actuates the indicator switches on the steering column, but the twisty headlight control is a switch in itself and wires travel down the stalk and onto a steering column plug. Which is lucky, because you can get at them. If you needed to take the indicator stalk off, you need to take the steering wheel off, and I don't like the idea of fiddling with things that have explosive airbags in them.
The trick is the tiny little tab on the indicator stalk where it joins into the column - pop that with a screwdriver and the cover comes off and all the wires are exposed! The greyish wire is for the headlight auto, the green wire is the headlight. I spliced a bit of extra wire in, soldered, with heatshrink, and then wrapped the whole thing in insulation tape. My theory being that these wires keep moving and rubbing every time you turn the indicators on or flash the high beams. But I think more importantly, the wires seemed light they'd had some heat damage, so I think the light in the keyswitch may have contributed to the breakage too.
With my extra wire and heatshrink and tape I couldn't fit it all back into the stalk to put the cover back on. In trying to force it back together, I broke the tab that keeps the cover in place. The 'ole falcon isn't trying to win any trophies, so I cable tied the cover back in place, job done. So tip: use small gauge wire and take it easy with the insulation.
Now, while initially using the internet to diagnose this problem, I found a dead link to a fordforums.com.au, item index 11268443, by paulie0735, which would have been great to have read instead of finding this out the hard way. Which is what inspired me to post this article. So if you were looking frantically for a copy of that article, but found this instead, then my job is done.