Howdy all,
While waiting on parts to arrive to get our Patrol on the road -- please Mr. Mailman, bring me a package, please? -- I've been tiding things up -- including some electrical stuff. One thing I did notice during the couple of night drives was that the headlights are dim. Okay, I need to be forthright, these were generator-less drives

However, even when the battery was fresh off the charger, they just weren't very exciting or spectacular. So Barritt and I started to investigate.
With the truck connected to a battery charger (to act as a generator during the test), we saw a 2.66 volt drop from the battery cable at the starter where we measured 12.47 volts to the left headlamp where only 9.81 volts arrived. That's some pretty impressive voltage drop

.
We wanted to see what kind of improvement was possible so we hot-wired the left headlight to bypass the entire circuit by connecting a short, somewhat thin, wire to the main, hot wire on the alternator. With that connection, the voltage drop reduced and 11.60 volts were available at the light -- not perfect, but a big improvement (12.4 volts would be ideal!)
We measured the right light's low beam output at 9.81 volts with our handy, dandy light meter: 15,400 LUX. At the same time, the hot-wired left headlight, running at 11.60 volts, was putting out 25,600 LUX. That's nearly double the light output!
Here's what the headlight circuit looks like with our measurements:
9.81 volts yields 15,500 LUX
11.60 volts yields 25,600 LUX
I'd really like to have all that extra light when puttering around in the Patrol... so I came up with some ideas. I think the best (sadly) involves cutting two stock wires. The stock headlight circuit takes the longest way possible to get from the power source at the fuse box all the way to the headlight. The route is:
Start at the fuse box, into the dash, to the headlight switch, down to the high/low beam foot switch, back up to the dash, across the firewall to the fender, crossing just under the fuse box, then onto the right headlight, then, finally to the left headlight!
I've decided that any reasonable person would wonder why there's no relay... I did, but then, am I being reasonable?

I mean, gosh, even the horn got a relay, but the headlights seem to have been short changed. Life's not fair!
On a side note, I do love the sound of the Patrol horns -- It's more of a happy "Hey there!
" and less "FU!
"
My plan is to break both the high and low beam wires where they pass near the fuse box on their long journey from the dimmer switch to the lights, splice in two relays using the headlight lines to power the relay coils. Attaching the remaining run-to-the-headlights to the relay. Finally, pulling a new, thick, wire from the main power buss on the fuse box, through a new fuse (will need to calculate this fuse size) and to the relay. The relays won't looks stock -- especially since I picked up some modern style 40a relays, but if I install them under the starter relay, they won't be too visible.
Here's my proposed modification:
You may have noticed the additional ground connections -- since many headlight issues are due to a poor ground, I was thinking that tying the headlights to ground closer would reduce the circuit resistance. In audio design, this kind of thing can cause all sorts of havoc -- ground loops -- but since the Patrol is far, far from from high tech, I don't foresee any issues...
but I could be wrong!
I've also cooked up another variation that does not require hacking up wires. Instead of a single pair of relays near the fuse box, install two pairs. One at each headlight terminal strip and then use the strip to "break" into the wires. You would still need to route a heavy wire from the source, through a fuse and to each relay, but at least that would be easily removable if you wanted to return it to stock.
Anyway, that's what I've been thinking about...
John