So that the power from hi beam will send power to fog lamps but the power from fog lamps will not back feed to the high beams. Use the following procedure.
Fog Lamp High Beam Mod Gm Forum Buick Cadillac Olds
How to wire fog lights to high beams. Connect the end of the circuit tester to ground and use the tester to locate the headlamp high beam lead. Wiring hid low beams and fog lights in my 04 tahoe and auto fog lights duration. A three way connection must be made joining the second wire from each of the fog lights to the red wire going to the relay terminal 87. Start by taping one end of the power wire to the metal bumper support. Show full signature. Turn on the low beam headlamps.
Power 12v to the fogs lights passes through the normally closed contacts of the relay terminals 30 and 87a. Terminal 87 is not used. The easy way to make this work. The power supply wire will run from the high beam relay wiring harness to the driving or fog lights. Leave at least one foot of wire hanging after the tape to leave enough slack for the connection to the lights. Wiring light bars to your high beams duration.
The fog lights each have two wires one for ground and one for the 12v power. Low beam operation is unaffected so you can turn your fog lights on and off and never lose control of your fog light switch when not using high beams. Connect the end of the circuit tester to ground and use the tester to locate the headlamp low beam lead. Put a diode between the high beam power wire and the fog light power wire. When the coil of the relay is energized 12v from the high beam switch to terminal 86 ground on terminal 85 the normally closed contacts open interrupting 12v to the fog lights. Add driving light slave to automatically illuminate an additional set of lights light bars ditch lights etc when the high beams are activated using your factory switch.
Turn on the high beam headlamps. Route the power supply wire. Turn off the ignition and the headlamps. One of these wires from each fog light has already been connected to ground.
Gallery of How To Wire Fog Lights To High Beams
