Registration and Posting Agreement
Another thing you can do for brighter headlights is to put in a headlight relay. On my '78 K-10 I used a "H4 9003 P43t relay harness" from Autolumination (scroll about 1/4 of the way down the page). This does not require any wiring changes, as it has a connector that mimics the back end of the stock headlight. The existing truck wiring controls the relay, and the relay drives the bulbs right off the battery. For a double stack, you may need two of these, or there may be an alternate relay setup. The point is to get the wiring from the battery to the bulbs as short as possible, with as few connections as possible, and get all the stock wiring and the headlight switch out of the power circuit, and just use that stuff to control the relay.They have headlights and baskets and bulbs as well, but I was unimpressed with [them].
Welcome to the site!Linked is the factory 1985 Wiring Manual (see pages 9 & 10), courtesy of hatzie.The headlamp switch knob is released by depressing a small metal button on the backside of the switch housing (see image).white (offset but adjacent to red) = controlled ground circuit from the dome and courtesy lamps (full CCW rotation of the headlamp switch knob grounds this wire to illuminate the interior lights).red = main B+ feed from the fusible link (hot at all times) - powers the headlamps only. The red wire feeds power to the non-serviceable circuit breaker integral with the headlamp switch.green = dimmer controlled dash lamp circuit that routes power to the redundant 5-amp "INST LPS" fuse in the fuse block. Rotating the headlamp switch knob varies the voltage on the green wire and instrument lamps fuse.Power into the instrument lamps dimmer comes from the 20-amp "T/L CTSY" lamps fuse via one of the two orange wires (details below).Power out of the instrument lamps fuse routes to the three "LPS" sockets located directly above the fuse and to the dash lamps via a gray wire.white (adjacent to green) = this wire position is equivalent to brown and may be used to power the cab roof lamps if you have that option.purple = this is actually "brown" and feeds all of the tail, park, marker and license plate lamps.yellow = feed to the headlamp dimmer switch. Red (B+) is switched by the headlamp switch and then power is routed directly to the dimmer switch for high/low beam selection.orange (x2) = one is power from the 20-amp "T/L CTSY" fuse in the fuse block (hot at all times). The remaining orange wire feeds unswitched B+ directly to the optional courtesy lamp mounted under the dash.Edit: In haste, I missed your attached image the first go 'round...