Written by: Clint Collins
This mod is for the 83-87 Trucks and 83-91 Suburbans
with the Dual Headlights System. This mod allows you to run all four headlights when you
apply the high beams.
4 Line Taps
1 Automotive relay (SPDT, 30 amps)
4 male red/blue connectors
4 female red/blue connectors
** red = small gauge wire & blue = medium gauge wire...either works **
First, use the test light to locate the following wires:
30 - Low Beam (+) wire
86 - High Beam (+) wire
87 - (+) source when lights are on
85 - Ground (-) wire
Second, connect the wires as indicated with the numbers corresponding with the wire and
relay. On my 87, I used the front blinker's set of wires...it was a 3 wire connection, a
ground, constant positive, and the other makes the bulb pulsate. With all of these wires
connected, when you turn on the headlights (low-beam) only your low's will work, with the
high-beams selected, all 4 will work!
Enjoy the fruits of my frustrating trial and error!