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Thread: help with wiring fog lights

  1. #1

    help with wiring fog lights

    i need someone's help with a problem i have. i have installed the dash switch and relay near the fuse panel and ran the wires from the switch to the relay (86) and from the parking lights to the switch. i also have correctly ran a wire from the main(high)beams to (85) on the relay, so the fog lights only operate with sidelights or dipped beamed. that leaves me with the wire from (87) on the relay, which should be power to the fog lights. first problem is, i dont seem to be getting power on this wire, even though i can hear the relay switching when pulling the fog light switch. next question, how do i wire up the fog lights correctly - in parallel, or series, or does it not matter. thanks.

  2. #2
    You should have 4 basic terminals on the relay. They're numbered 85, 86, 87 and 30.

    Terminals 85 and 86 make up the control circuit. Terminals 87 and 30 make up the power or contact circuit. When current goes through 85/86, the control circuit is energized or electromagnetized (there's a coil of wire between 85 and 86 inside the relay housing). This causes electrical contacts inside to close and connect 87 and 30.

    There are several ways of wiring the components to the relay, but you want your fog light switch to control battery current through terminals 85 and 86, then to ground. This is a relatively low-current circuit, so you can use relatively small gauge wire (14-16 ga.). Another variation is to place the switch on the ground side of the relay. Make sure this circuit (all circuits) is protected by a fuse of the appropriate size. When the switch is ON, you'll hear the relay "click".

    Now the connection to the fog lights. Use heavier, 12-14 ga. wire in this circuit as more current will be needed here (and the main reason to use a relay in the first place). Connect a wire either directly from the positive battery terminal or from an unused (or seldom used) fuse holder in the fuse box. Connect this wire to the fog light wire. Create a branch circuit at some convenient location so there's a current path to each light. Take the fog light ground wires and connect them to a good ground location (bare metal, tight connection).

    The above description controls the fogs independently of the headlamps. If you want the fog lights to come ON whenever the low beams are ON, splice into one of the low beam wires to energize relay circuit 85/86.

    I suggest you purchase a relatively inexpensive 12 volt test light so you can verify there's voltage where you think you should have it. Remember to disconnect the battery before you attempt any wire connections to source voltage.

    Hope this helps,
    Sherwood Lee

    9/29/02 rev.
    This may be obvious, but I forgot to mention the contact circuit connections from relay to fog lamps. Connect source voltage wire to relay terminal 87 or 30, your choice. Connect wire from the other terminal to the fog light branch circuit.

  3. #3
    just beautiful, Sherwood!

    71 911S Targa

  4. #4
    thanks for your help. i was able to wire up the fogs so that they are on with the dipped beams or sidelights, and when the high beams are switched on, the relay interrupts the circuit. i took power from an unused fuse into 30, then split the output from 87, and then thru the inside fenders to the fog lights. works perfectly. thanks again.


  5. #5


    Ok, no response on the Pelican board, so I'll try here:

    <cut & paste>

    just got a fog lite switch for my 911. Its a 914 part, and since I dont own a 914, no manual. The parts diagram is too small to read.

    How do I connect it? Im using a relay w/100W H3 bulbs(I think).
    The back of the switch has 4 terminals:

    NR at the 10 oclock position
    N at the 12 position
    58 at the 2 position
    - at the 6 position
    71 911S Targa

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