Z31 Fog Lamp modification

This mod is to allow the fog light to work independently from the headlights. It utilizes the stock fog light switch, but the fogs will work with the parking lights instead of the headlights and stay on with the high beam. It is a fairly simple and straight forward mod.

The 1st thing that needs to be done is to locate the fog light relay and determine which wire is the trigger wire.

The Fog Lamp relays are located in the Relay boc under the hood.

One should be constant power and the other should be switched power when the headlights are on or off.

At this point we need to get under the relay box where all the wires are. You will need to remove the screws holding the coolant overflow and move it out of the way to gain access to one of the screws holding the relay box in. Once the coolant overflow is out of the way and the relay box is unbolted, flip the box over and find the switched wire for the fog light relay. It should be a smaller orange wire with a black stripe.

Cut the trigger wire and tape off the end to prevent any sparks or shorts form happening. Make sure to leave enough wire on the fuse box side to tap into. Here You can see the orange with black stripe wire cut, one end taped off and the end of the new power wire

Next, you will need to run a single wire from the fuse box out of the engine bay and into the passenger front fender/wheel well area. In the passenger fender you need to access the marker light connector and wires. 2 wire system, one red for power and one black for ground. The new power source for the switch side of the relay will be coming from the red wire here. You can use a wire tap here or you can cut the red power wire and use a butt connector to put it all back together like I did.

Once the wire has been ran and spliced into the power side of the marker light, you need to connect the new wire to the old wire in the relay box.

At this point you can put the relay back in and test it out. The fog lights should work without needing the headlights on and you should still be able to turn them on and off with the stock switch. Once it's all tested and working, go ahead and put the relay box and coolant overflow bottle back in to place and you're done!

Additional pictures of how and where I ran the wire myself. You can run it however you want but the way I did it is not even noticeable and no one can anything has been done. And how it looks afterwards with the lights on.

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Written by: Keif Potter