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Wiring For 4 Headlight Operation in High Beam .

A lot of people are installing projector headlights to their 30Xs that operate a different light fixture for high / low beams, ie the headlights have two lamps per headlight rather than the standard one lamp.

 Following is a description for modifying the wiring so as all four headlights are illuminated when high beam is selected. It is much easier to carry out parts of this modification prior to the headlights being installed on the vehicle.

 I have used the logic that the car is designed to have either low or high beam selected, not both at once. Therefore this method is designed to not place excessive electrical loads on existing equipment. All modifications are limited to the aftermarket headlight and does not alter the OEM headlight circuit. This means original headlights can be reinstalled without the risk of creating a fault where both filaments are powered up simultaneously.

 It a simple electrical circuit that supplies power to low beam when high beam is selected. This is achieved by power from the high beam circuit operating a relay coil to close a contact and supply power back to the low beam circuit.

 *Note – It is only necessary to make these changes to one headlight only.

 Tools Required:
Soldering iron
10mm spanner or socket
Drill / cordless screwdriver

Materials Required:
2 metres x 20 amp cable
4 x spade lugs to suit
1 x large spade lug (or 1 x crimp lug plus fusible link with 20 amp fuse)
* 1 x 20 amp square fuse (if no ABS, see below)
1 x 12 volt 30 amp relay
1 x self tapping screw
Cable ties
Insulation tape




Step 1:

Cut 3 pieces of cable approximately 200mm (8”) long, crimp a spade lug to one end and strip the other end approximately 20mm (3/4”). If you’re using the same coloured cable, label each one with a piece of tape or similar so you can easily identify each wire. This will make it easier when you connect them to the relay.



Step 2:

* Use the headlight closest to the fuse box.

Identify which cables in the new headlight are low beam, high beam and ground.

Pull back the insulating boot on the plug and strip the insulation from the cable as shown. Feed the 3 new wires through the boot end, twist around the applicable headlight wire, solder, insulation tape and slide the boot back on.



Step 3:

Mount the relay on the headlight casing as shown using a self tapping screw.

Connect the 3 wires previously installed to their appropriate male terminal on the relay:

Ground to the negative side of the coil (usually terminal 85)

High beam to positive side of coil (usually terminal 86)

Low beam to one side of the contact (usually terminal 87)



Step 4:

Install headlight if it is not already installed.




Step 5:

Cut a piece of cable long enough to reach from the relay to the fuse box, install a spade terminal to one end and connect to the side of the relay contact not yet used (usually terminal 30).

Route the cable to the base of the fuse box and cable tie as desired



Step 6:


There’s two methods here of picking up a 12 volt source depending if you have got ABS. I don’t so I did the following:

Remove 10mm nuts securing the secondary fuse box.

Install large spade lug to new cable and plug onto male lug below the unused ABS fuse.

Replace 60 amp square fuse with 20 amp.

Refit secondary fuse box.

Reconnect battery. Done!!!



If you have got ABS so don’t have a spare fuse do the following:


Install an in line fuse to the end of the new cable with a 20 amp fuse.

Install a crimp lug to the other side of the fuse holder cable and connect to the power supply to the secondary fuse box.

Reconnect battery. Done!!!