I now have most of the parts in hand that I need for phase 2 of the '03 Ranger lighting upgrade: the relay mod.
What’s a relay mod you ask? Vehicles equipped with halogen headlamps often have wires that are simply too small to supply adequate current to their headlamps, reducing output well below what they are rated for. The automakers do this to save money - thinner wires are cheaper and they’d rather just switch the power through that switch on the dash/stalk than use relays. It’s common to use 18 and 20 gauge wires for this task rather than the 14+ gauge wires you really need.
By installing relays, you can improve the brightness of your headlamps markedly using otherwise OEM parts. Daniel Stern explains this well and offers fantastic customized customer service should you be interested in this yourself.
Here’s a sketch of how I plan on implementing this scheme on my Ranger:
Ordinarily, the factory harness just plugs into the headlamps. For this modification, I will preserve the factory harness but use it to control the relays that switch power to the headlamps via much shorter wire runs via heavier-gauge wire.
Using fuses on both sides of the relay is a tad silly, but I happen to have a 6-position fuse block and that’s how I sketched it in. In reality, I’ll likely reduce it to the HI and LO common fuses for simplicity’s sake, to reduce the number of contacts I have to make, and to save 'block capacity for future projects.
Next up: finalizing the design, sourcing wire (16/18 gauge for signalling and an appropriate heavier gauge for power) and nailing down wire lengths for the actual harness layout.