1 x Reel of automotive electrical wire (no, you do not need a whole reel, but
wire always comes in handy anyway)
1 x Simple SPST switch (Jaycar stock code SK0975)
Something to strip/cut wires with (I prefer to use a Swiss army knife)
1 x Flat head screwdriver
1 x Soldering iron and some tin solder
1 x Electrical tape
Okay, lets get started!
This is a basic wiring diagram of what we will be doing:
Normally each light is powered by its
own power line. Hence the brake lights and fogs operate individually of each
other.
But if we divert power from the brake
lights to the fogs, then they will come on when the brake is pressed. The switch
lets us disable the modification and return to normal functioning while the
diodes ensure electricity does not flow in the opposite direction.
Step 1: Preparing the
wiring
a. Cut 3 lengths of automotive wire, each about 60-70cm long.
They need to be long enough to allow for opening and closing of the boot
lid
b. Strip approximately 2cm of the insulation from each end of all of the
wires
If you have never soldered before, just follow
the image to the right....
c. Now you will need to solder the end of one wire onto one of the terminals of the
switch
d. Grab the other two wires and solder one end
of each wire onto the other terminal of the switch
e. Okay, now we need to add some diodes. A diode
acts like a one way valve for electricity flow. We need these to prevent
the light bulb error indicator from appearing on the dash. If you look at
the diode you will notice one end has a line. Electricity flows in the
direction towards the line.
First we will be working on the wire pictured
below (the single wire attached to the switch)
We need to add the diode mid way along this wire
as shown. To do this, simply cut the wire in half, remove about 2cm of the
insulation from the two resulting ends, and then solder these onto the
arms of the diode. Please note the orientation of the line on diode in
relation to the switch.
Now we need to add diodes to the two remaining
wires.
However these will be added to the ends of the
wires. Solder the end of each wire onto a diode as shown below. Again note
the placement of the wire in relation to the line on the diode
Step 2: Okay, now its time to actually
connect this to the car!
a. Open up the boot. On the left arm there is a
plastic shield covering the underlying wires. To remove the shield, there
are three plastic 'rivets'. Push in on the centres and then just pull them
out. The shield will then pull easily away from the boot arm to reveal
this:
b. To get to the actual wires, use your Swiss
army knife to gently cut into the wiring loom and pull back the cover. You
will need to open up at least 10cm to work with it easily
c. Find two wires of the same colour: Green
with a brown stripe and silver markings. These wires deliver power to
the left and right fog lights.
d. Cut one of the wires and remove some of the
insulation from each end to get this:
e. Now grab one of the diodes pictured here:
and solder it to the wires as such. Note the
orientation of the line on the diode!
f. Repeat steps d and e for the other wire
g: Now we need to make the final connection to
the brake light. To get to the wires, you need to remove a small portion
of the boot liner. Use a flathead screwdriver to pop out the two plastic
rivets and then simply pull the edge of the boot liner away. Look down
behind the rear light and you should see the wiring loom.
h. Disconnect the plug and cut some of the
plastic sleeving away. Find the green wire with white stripe and
cut away some of the insulation to reveal the bare wire underneath.
i. Solder
the last remaining wire so you end up with this:
j. Okay, now to test the setup plug the wiring
loom back in and then press on the brake (obviously make sure the switch
is set to the on position). The rear fogs should light up with the main
brake lights. Now turn the switch off and the lights should not light up
with the main brake lights. Finally, turn on the headlights and press the
'rear fog' button next to the coin holder and the fogs should stay on as
per normal. If everything works, cover the bare wires with electrical tape
and tidy everything up
