European Rear Fog Light Activation
The Mk IV GTI's all come with the
optics and bulb fixtures to install rear fog lights. They are not fog
lights like the ones up front... they look more like really bright brake lights.
There are two ways these fogs can be hooked up. I started with them hooked
up to work along with the brake lights. They can also be wired to be
activated by the European spec light switch. Last weekend I wired them up
so they worked through the European headlight switch. I may
try a hybrid of the two. It would be nice to have them activate with the
brake lights and then be even brighter when they are switched on as fogs.
I'll have to find out if there is some kind of diode that will only let the
voltage flow one way so the brake lights don't go on when I activate the rear
Update! It works! I
got the rear fogs to work both with the switch in the dash and also with the
brake lights. Click here to see how.
Below are some photos of what they
look like when they're on:
The lower lights below the tail lights are the euro fogs.
The rear fogs when combined with the tail lights are pretty
Tuning has a good set of installation instructions. According to the
laws in the US, it is only legal to activate the drivers' side rear fog. I
activated both for better visibility. If I get a ticket, then I'll look
into disconnecting the passenger side.
Okay, I did a little research, bought a few diodes, and got the
lights hooked up so the rear fogs work both as brake lights and as rear fogs.
The install is quite easy. This used to be based on the How2 section of
www.vwmkiv.com 's web site. That site is no longer around. I'll do my best to
write up how to do this install.
- Euro headlight switch
- 20 ft or so of 14-16g wire
- 3 diodes (Radio Shack Model 276-1144) pictured below.
- shrink wrap.
- VW wiring harness 000-976-126. Its a little yellow wire with a connector
on each end. Since I wanted to activate both rear fogs, I purchased two of
them. I think it cost around $3 each.
- tail light bulbs (P21W). They come in a package of 2 normally.
- Small female crimp connectors (4.8mm/.187" tab) You'll need 4 of these.
- One quick connect wiring splice (optional). You can solder the one wire
connection if you prefer.
- Soldering Iron
- Wire cutters (diagonal cutters)
- Wire strippers
- Heat gun (for the shrink wrap)
These are the correct diodes. I got them for $1.50 at
There are a few main steps to wiring your rear fogs. What I'm
describing will allow you to use your rear fogs as extra brake lights and as
rear fog lights activated through the euro headlight switch.
The first part of the installation will activate the rear fogs
along with your brake lights. This part is very easy.
- Cut 2 -8" lengths of 14 or 16GA wire. Attach one of the small female connectors
to each end.
- Cut each of these wires in half and strip each open end. You'll need to
solder a diode in the middle of each of these jumpers. It will look something
like what you see below.
Close-up of Diode Installed.
I soldered it in the middle of the jumper. Make sure you
mark which end has the silver stripe on the diode. This side must be
pointing towards the rear fog lights when you install it. Otherwise the
flow of electricity will not be in the correct direction.
Pic of the whole jumper.
I used shrink wrap on the jumper to keep it from shorting out.
The dude at Radio Shack said these diodes are low enough amperage that they
don't heat up enough to need to be out in the open air. He said the shrink
wrap wouldn't overheat them.
Final shrink wrapped diode
- You're now ready to go to the car. Remove the two interior panels that
cover the backs of the tail lights. There are carriers that hold the bulbs
that plug into the back of the tail lights. You'll see the wiring harness
plugged into them.
- Unplug the wiring harness and then remove each of these bulb holders. You'll
see two tabs that you squeeze together to release the bulb holder. It takes
a bit of wiggling to completely remove them, but be patient.
- Install the new bulbs in the blank spot on the bulb holder.
- Turn the bulb holder over. You'll see that there's a male spade connector
on the back up near the brake light (at the top) and behind the rear fog
light (at the bottom left for the passanger side and bottom right for the
drivers side). Install the jumper that you made between these two male connectors.
Make sure that the silver band on the diode is pointing towards the rear
fog light. This will allow the current from the brake light to go to the
rear fog, but it won't allow current going to the rear fog to activate the
- Remove the blank cover that is over the hole for the rear fog bulb on the
tail lights. Its just a plastic tab that covers the hole. Try not to drop
it down into your tail light. It isn't the end of the world if you do, but
it will rattle around in there for all of eternity. You can now re-install
the bulb holder in the car.
- Plug the wiring harnesses back in. Test the brake lights at this point
and make sure that the fogs light up with the brake lights. If they don't,
you probably got the diode in backwards. Remove the jumpers and install them
the other way.
- Unplug the wiring harnesses again since we're going to work with them again.
Now its time to wire up the euro headlight switch.
- Remove your headlight switch. Do this by pushing in on the switch part
and turn it to the right. You can then pull the whole switch housing out
of the dash. Unplug the wiring harness.
- Cut the VW wiring harness (the yellow wire with a connector on each end)
in half. Strip the non-connector end and solder one to one end of the long
14ga wire. I shrink wrapped the solder joint. Electrical tape will work.
- Look at the back of the Euro switch and locate the terminal labeled "NSL".
Its embossed on the inside where the wiring harness plugs in. Now look at
the wiring harness and find the empty plug over the "NSL" terminal. Plug
the wiring connector into that slot on the wiring harness.
- Open the fuse pannel inside the drivers door. You should then be able to
route the wire down the side through that pannel to the trim along the running
board. leave a little slack.
- You can then plug the wiring harness into the back of the headlight switch
and re-install that.
- Route the wire along the door sill. Slip it under the carpet under the
rear seat and under the carpet and panel cover till it gets to the rear drivers-side
- You'll need to solder in the third diode into the line here. You'll want
the silver line on the diode facing the tail light. This will make it so
the LED in the euro switch doesn't light up every time you hit the brakes.
***(Optional: I installed the diode using male and female crimp connectors
in case I got it backwards. That way it was easy for me to flip it around
if I needed to).
- Solder the other end of the VW Connector to the silver band end of the
diode. Shrink wrap over the diode to protect it.
- Look at the wiring harness for the rear tail light to see where the empty
connector slot is. Install the connector that we just soldered in the empty
slot. Plug in the wiring harness to the bulb holder.
- To activate the passanger side fog with the headlight switch, you need
to run a wire from the drivers' side to the passanger side. I found it easier
to do this in reverse. Take half of the second VW wires and solder it to
the end of a lenght of 14ga wire. You'll need about 6-8 feet. Wrap the solder
joint in shrink wrap or electrical tape.
- Plug this connector into the blank slot on the passanger side tail light
wiring harness. Plug the wiring harness into the bulb holder.
- Route the wire from the passanger side to the drivers side. I just threaded
it out from the side compartment and wedged it under the plastic molding
that covers the back portion of the trunk. I threaded it under the edge of
the side compartment on the other side so it met up near the rear tail light.
- I used the quick connect here to splice the wire from the passanger side
into the wire coming from the headlight switch. I did this BEHIND the diode
that we installed (meaning between the diode and the tail light).
- Wrap whatever connection you make in shrink wrap or electrical tape and
you should be ready to go.
- Test out the wiring. If the brake lights turn on the LED in the dash and
the readlight switch doesn't turn on the rear fogs, then you've got the diode
on the line between the headlight switch and the tails in backwards.
To activate your new rear fogs, you'll just need to pull on your headlight
switch. One click turns on the front fogs. Two clicks turns on the rear fogs
I'll add some photos to this tomorrow. Hopefully that wil be of some help
to you. Let me know if you've got questions.
E-mail me if you've
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