This modification will change the operation of the (otherwise useless) fog lights. They will automatically turn on when you start the car. They will stay on with the parking lights. When you turn on the headlights, they will revert to normal operation.

These instructions were what I did on my 1995 Mystique. Hopefully, there haven't been too many changes in newer models.

Complexity: Moderate

Skills Required: Some electrical and soldering knowledge very helpful.

Requirements:
12VDC DPDT relay (Radio Shack cat.# 275-206, approx US$6.49, or equivalent) The relay pin numbers shown in the instructions below are for the Radio Shack relay. The relay is mounted to a socket.
Wire (18-20awg)
Voltmeter (to verify connections)
Soldering supplies, electrical tape (recommended) or wire taps and connectors.

How the fog lights are currently wired:
The fog lights are controlled by a small white relay located under the dash, behind the headlight switch.

One side of the relay contacts (Orange/Black) are connected to a CONSTANT +12V through Fuse 5 (in the Power Distribution Box under the hood), rated 15 amps. The other side (Orange/Yellow) goes to the indicator in the headlight switch, and the two fog lights (it changes to Orange/Blue for some reason). The other side of the fog lights are wired to ground (Black).

The wiring for the relay coil goes through THREE switches! One side (Black/Red, although the Red looks more like Brown) is connected to ground through the main fog-light switch, the one you control by pulling the switch in and out. It is tied to ground when on, open when off. The other side is connected , through two switches, to a CONSTANT +12V through Fuse 26 (in the Fuse Junction Panel, in the dash), rated 20 amps. The first switch (Orange/Black) is the headlamp switch. Power is supplied only when the headlights are on. The wiring then goes to the turn signal/high-beam (Orange/White at the headlight switch, Orange/Green at the turn signal) switch on the steering column. This removes power from the relay if the high-beams are turned on. The wire from the turn signal switch to the relay is Orange.

What will be changed:
The wiring for the relay coil will be altered. When the headlights are off, the relay coil will be connected directly to ground and +12V, turning it on. The +12V comes from a source that is only on in RUN and START. The ground comes from a good chassis ground. When the headlights are turned on, a relay will change contacts and restore the original wiring path.

Procedure:
View and print out this drawing to get an idea of the wiring, and where some connections will need to be made.

Use a 9/32 socket and remove the 5 bolts holding the dash panel below the steering column. Three of the bolts are under the mini-glovebox. One is under a small plug. Be careful, there is a light socket for the footwell light connected to it! Remove the light bulb socket and put the panel aside.

Behind the headlight switch, there should be a white relay. This is the fog light relay. Turn the fog lights on and off and verify that you feel it click to make certain it is correct. You will see 4 wires connecting to it. A thin Orange and Black/Red stripe for the relay coil, and heavier Orange/Black (12V in) and Orange/Yellow (switched output) wires. The fog lights are on a 15A fuse, and (WARNING!!) the +12V is ALWAYS live.

Splice in a wire to the thin Black/Red stripe wire (the red strip may look more like brown). Connect the other end to the Normally Closed (NC) terminal of contact set 1 (pin 1) on the relay. Connect the common (COM) terminal of contact set 1 (pin 9) to a wire that will be tied to ground. To test: turn on the headlights, but leave the fog light switch OFF. The fog lights should turn on and off as you connect/disconnect the wire on the COM terminal to/from ground. The relay bypasses the fog light switch, which switches the ground side of the fog light relay.

At the fog light relay, CUT the thin Orange wire. Connect the wire going TO the relay to the COM terminal of contact set 2 (pin 12). Connect the other cut wire to the Normally Open (NO) terminal of contact set 2 (pin 8).

Find a thin wire in the fusebox that is Purple/Black. It is located in the lower-left connector next to the relays. It in the 'right' row, about the third one up. See the drawing for pictures on where it is located. This wire is live only in Run/Start. Splice in a wire to it, and connect the other end to the NC terminal of contact set 2 (pin 4). To test: Turn the ignition to the run position. The fog lights should turn on only in Run or Start. They should be OFF in all other positions. The high/low beam switch should have no effect.

Look for a thin Orange/White wire in back of the headlight switch. This is live whenever the headlights are turned on. Splice in a wire to it, and connect the other end to one of the relay coil terminals (pin 14).

Wire the other relay coil terminal to a wire that will be tied to ground (pin 13). If you use the Radio Shack relay, you can thread the same wire through both the coil and COM terminal (pins 9 and 13) and eliminate a separate wire. Connect the ground wire(s) to a good chassis ground.

Test your work: The fog lights should be off when the ignition is in Lock, OFF, and ACCessory positions. They should turn on in RUN. They should stay on when you turn the parking lights on. They should turn OFF when the headlights are turned on and be controlled by the standard fog light switch. With the headlights off, the high/low beam switch should have no effect. The fog lights should NEVER be on with the high beams (illegal.)

Carefully wrap with electrical tape, or heat-shrink, all connections. Return the fog light relay to wherever it was mounted (mine was just hanging from some wires!) Find a secure place to mount the new relay and secure both it and the wires.

Reinstall the dash panel. Don't forget any plugs covering the screwheads.

Options:
If you want to play dangerous, you can permanently lock the fog lights on by wiring the Black/Red wire to ground, and the fog light relay side of the cut Orange wire to the Purple/Black. This will allow the the fog lights to be on with the high beams, which is probably illegal (more than 4 lights on at a time.)

If you wire the relay coil to a Red/Black wire behind the headlight switch, instead of the Orange/White, the fog lights will turn off and act 'normal' when you turn on the parking lights.

You can use two separate relays if you want. Just wire both coils identically.

Notes:
Do NOT try to force the Orange/Yellow wire to 12V. I was hoping to be able to not cut any wires, but when you try to force it to 12V, the add-on relay buzzes. The Orange/Yellow wire is also used to power the high-beam switch and relay.

The fog-light indicator on the headlight switch will turn on and off with the fog lights. I couldn't see well enough to tell if it's wired or built in. It would require a separate relay if you wanted to keep it off when in DRL mode.

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E-mail me if you have any comments or questions.

(This page updated Aug 23, 1998.)