Rear Fog Light Install on North American Car

(This page was reprinted from: http://www.bme.med.ualberta.ca/~nicola/rear_fogs.html)

Introduction

Disclaimer

• Liability: the author (me) assumes no responsibility for the modifications you do on your car. Although to my knowledge these instructions are accurate, this includes any errors that these instructions may contain, any differences between your car and mine, as well as any errors in following the instructions. If you don't feel comfortable working with automotive electrical wiring I suggest you let someone with some experience do these modifications.
• Warranty: the modifications described in this document will probably void any manufacturer's warranty you may have left on the car. You assume all responsibility if your car is still covered by warranty.
• Proper use: rear fog lights are meant to be used in low-visibility conditions. Do not drive around with them all the time as you will blind those behind you and possibly risk trouble with the law.
• Local laws: laws in your country/state/region/whatever may not allow you to modify systems such as the external lights on your car, the penalty being at least a fine. Please check with your local authorities to be on the safe side.

Results

Position Light (5W)	Brake Light (20W)	Fog Light (20W)

Tools, Hardware and Suppliers

Choices, choices...

• If you don't want to worry about fog lights for now you can skip steps 3 and 5 below and basically modify the wiring according to figures 1 and 2.
• Do you want one fog light (driver's side) like stock VW's or two (one one each side) like other European cars (FIAT for example)? I chose the latter because I find that with one light it's confusing to those that follow.
• Would you rather snip wires (easy) or pull out the single contacts (difficult, can cause damage to connector if you don't have the proper tool) when rearranging the wiring in the rear lights harness? I chose the pulling method because the end result is neater and there is less crimping/soldering to do later. It requires some patience, though, because without the proper tool you have to insert two pieces of metal wire of the correct size (thick straightened paper clips should work) on either side of the contact from the connector side (as opposed to the wire side), in order to push the two metal "dogs" (springy clips) inwards far enough to disengage from the plastic housing. You will inevitably hack up the connector housing a little in the process, but once you get one of them out it's easy to learn how to do this efficiently.
• Do you prefer crimping wires together (easy but can look messy) or soldering (more reliable, takes skill)? Again I chose the latter because I wanted a reliable, clean-looking job and I know how to solder well.
• If you don't have a two-fog-position Euro lights switch, where do you want to get the power for the rear fogs? If your car has front fogs, or your switch does come out one notch when you pull on it, you can connect to the front fogs in the wiring, or you can modify the switch so that the power comes out from the pin that is assigned to the rear fogs in the euro version; that way if you're thinking about buying the euro switch later on you don't have to undo any wiring and just plug it in. Either way, rear and front fogs (assuming you have them) will come on together. You'll have to use a separate switch and find a place for it if you want them to be completely independent (I won't cover how to do that).

Getting Started

Removal of sill panels

The rear lights wiring harness runs under the driver's side sill panels (right by the door), which will have to be carefully removed and later replaced to get at the wires underneath. This is actually easy to do, but it's not easy if you don't know the trick. Simply apply pressure downwards on top of the sill and the bottom end should disengage the groove that was preventing it from rotating towards the seat as well as moving upwards. Once the bottom lip has been disconnected along the whole length of the sill, simply pull up on the sill and it will slip off the remaining clips that are holding it in place. Underneath you should see bundles of wires and the power locks air hoses held neatly in place with plastic clips.

Relay installation

If you already have the relay (position 10) and fuse (15A, also position 10) you can skip to the next section. If not you need to get them (I don't reccomend jumpering anything: both of those devices are there for a reason), and you don't necessarily have to get scalped by the VW dealer. You can buy general purpose relays at automotive parts stores that have the right pin configuration, with maybe an extra pin that you can bend off. Just make sure the relay will handle at least 15A of current, and that the coil is rated for 12V automotive use.

A Note on Pulling Out the Contacts

I'll try to explain how to do this the best way I can without pictures... OK, if you look at the contacts side of the connector (end opposite the wires) you'll see that the hole in the plastic where the contact "lives" has a cross or "+" shape. On one segment of the cross (say the horizontal one) you can see the actual metal contact, while above and below it are two empty spaces corresponding to the vertical portions of the +. That's where the paper clips/tiny screwdriver/finishing nails or whatever works best for you should be inserted--in BOTH of them simultaneously. Then you have to try and exert GENTLE pressure with the 2 paper clips (if they're not exactly the right size) simultaneously in such a way as to push the little dogs toward the contact so that they'll clear the plastic lip that is holding them back; at the same time you need to pull on the wire behind so that the contact will be ready to slip out, but not too hard or the dogs will dig themselves into the plastic making removal impossible. Once they clear the lip you're home free and the contact should slip out quite easily. Unfortunately you'd need about 4 hands to do this smoothly, so it might be a good idea to have someone help you hold the connector and pull gently on the wire while you play around with the paper clips on the other side.

Also, if the paper clips are exactly the right size (they fill the hole perfectly without play), all you really need to do is push them in. This should be enough to allow the dogs to bend in enough, otherwise try exerting slight pressure (this is where nails that are cut so they don't have a sharp point, or small screwdrivers, work well because they don't bend) to create leverage that will tend to bring the ends (that are inserted in the connector) closer together (you are trying to apply pressure at the back of the connector).

It might be helpful to buy one of these contacts just to see how it's made to help you apply pressure in the right places. The dogs are essentially two springy metal clips that bend away from the contact once it's inside the plastic connector housing.

This is a bit like lock-picking, in case you didn't notice, but at least you CAN legally buy the tool that makes this job much easier...:)

The Switch End

The Tail Lights End

1. (c.f. figure 1) The first thing to do is disconnect the connection to the outermost socket (one of the two tail lights in the NA model, the one labelled brake light above) so that it will be free to use as a brake light. It was #3 on my driver's side light (big, 8-pin connector, terminal T8d/3) and #8 on the passenger's side (again an 8-pin connector, terminal T8e/8). Here is where you decide whether you want to try and pull the little metal contacts out of the connector, or just snip the wire, leaving enough so that you'll be able to connect to it later. Do this on both sides of the car (red "cut" marks in the figure), and notice that the two connector arrangements are different.
2. (c.f. figure 2) Then you find the wires that carry power to the brake lights (#8 on driver's side, T8d/8; #3 on passenger's side, T8e/3); if you're going the snipping route, cut again here and leave enough wire for later. The brake lights wire that was connected to T8d/8 can now be connected to T8d/3 (snipped in the preceding paragraph). Otherwise pull out the contact and push it back into T8d/3.
3. Connect the new wire from your switch to the position where the brake lights used to be on the driver's side (terminal 8 of the 8-pin connector, T8d/8 in figure 2). This will be the driver's side fog light.
4. On the driver's side rear lights unit there is also a smaller connector (5-pin, called T5d in fig.1) that connects to wires that end up in the passenger's side lights unit (passing on the lower rear edge of the trunk space). These connections also need to be modified to properly connect the brake lights since we have moved things around. I have indicated in figure 2 in blue the new terminal positions for the brake lights. To make these changes, remove the contact from the1-pin connector T1v (drivers side) and insert it into the 5-pin connector at position 1 (T5d/1).  Save the 1-pin plastic connector to be used later on the passenger side. The spot where the 1-pin connector used to be on the driver's side is no longer used unless you want to add a second fog light (see next step). Now, on the passenger side, remove the third brake light wire (position 2 of the 3-pin connector on passenger's side, T3e/2).  Insert the contact into the 1-pin connector we removed from the drivers side and connect it to the passenger side which now connects to the assembly using the 1-pin connector (I've labelled this terminal T1v in the diagram although its official VW name is probably T1w).
5. If you also want to take power to another fog light on the passenger's side it will require adding an extra wire to the bundle that joins the two rear light assemblies. I have not shown this wire in the diagrams, but it should take power to terminal T8e/3 (it basically follows the same course as the old brake lights wiring). The other end of this wire splices to the new wire that comes from the headlight switch or connects to terminal T1v (the one that was left unused in the previous step; you'll need to buy a new connector housing for it to snap in properly).
6. Insert the proper wattage bulbs as indicated by the pictures above. You may need to enlarge a hole in the back of the passenger's side plastic reflector for the larger 20W bulb (brake light) to go in; use a drill and/or a round file and try not to get too many plastic filings in the optics. Check that each bulb does what it's supposed to.
7. Drive around and show off the results to your friends :)

Figure 1: Position lights wiring diagram--two of them will be converted to brake lights	Figure 2: Brake lights wiring diagram--all the necessary changes for the European rear lights arrangement

Note: the 1995 m.y. and later cars should already have an unused wire coming from the fuse/relay panel (connector K10) that can be used instead of running another wire from the switch to the lights. It is one of two wires that connect to T8d/8, while the wire actually carrying power to the brake lights is snipped and connected to T8d/3 as in #2 above. Since you're going to be working behind the fuse/relay panel anyway, you can find it by checking the colors of the wires that come out of connector K (I'll see what color the wiring diagrams say but they can vary, so you may want to take your chances and snip randomly). The fog lights switch (position 12) should then be connected directly to connector P6 in the fuse/relay panel instead of running a separate wire all the way to the back.

The (Optional) Fuse/Relay Panel Bit

Modifying the Stock NA Switch

Parallel connection:

Switch cam hack:

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