Rear fog light install- a new approach, some help needed

[RDM]

I have wanted to install a rear fog light in my car as long as I have had it because, well, it's foggy here and I'd rather not get hit. And I think rear fogs are cool. I initially started out on the traditional path. I found a foglight at a swap meet. I found the wires that go to the foglight under my rear fender. I wasn't crazy about the inelegance of drilling a hole in the valance and dangling a light down there all by itself, but that was the price to pay to get what I wanted.

Then I read an article in 911 & Porsche World that said Autofarm (a high-end UK Porsche garage) put a red LED bulb in the passenger-side reverse light housing and connected that as a foglight. Much cleaner, and in line with many of the European cars that have a reverse light on the passenger side and the rear fog light in the corresponding location on the driver's side.

I let that simmer for a while, until another inspiration hit. Spoke began making LED boards for reverse lights (see LED Brake Lights), and I was able to acquire a set with the left side board red LEDs, the right side white LEDs from him. I already had the tail/brake light boards, and was very pleased with them, so this wasn't really a gamble. Here's what we're starting with (just because I like this picture!)



Start from here. Remove three screws, take off the lens.



For the passenger side, it's simply a matter of taking out the reverse bulb and plugging in and tightening the (very bright!) LED board. You can see the installed tail/brake board as well.



On the driver's side, take out the tail light bulb (far center) and the reflector (far outside) to remove the tail light housing.



Behind the tail light housing, you might find a set of wires like this:



Hard to tell what color they are (were) and which is for power and which wire is for ground. Neither responded to the foglight switch.



Remove the two screws holding the cover on the back of the tail light housing. It will take some tugging to open it up due to the putty that Porsche uses to seal up the housing.

Note how dirty the outside is and how clean the inside is. It's important to maintain a watertight/dirt-tight seal on re-install. Fortunately, my local parts store had the putty on the shelf.



So here's the inside of the light housing. On the left is the tail/brake light, then the reverse light, then the ground wire.



After the ground wire comes the blinker, then the side marker light (with the green wire). If you run yellow lenses, the green wire should be disconnected from the tail light and connected to the blinker.

[RDM]

Disconnect the white wire with black stripe from the reverse light socket. I bundled it and taped it thoroughly in case someone wants to go back to stock or my experiment fails.

The next question was how to get the fog light wire into the light housing. There didn't seem to be an obvious way to join it with the existing wire bundle, so I drilled another small hole, grommeted the wire as best I could with electrical tape, then sealed inside and outside the housing with putty. I crimped (Opinions on Wire Crimping vs Soldering vs Both).

I'm pretty sure someone on the board can offer a better solution for protecting that wire, and I'm not against going back in and redoing what I've done if that seems sensible. Suggestions welcome here.

Due to the tail light housing being grounded and therefore only one wire going to the reverse light socket, the ground wire in the fog light harness isn't being used.

Now for the questions

1. Which switch?

A. In a thread about wiring the rear foglight (911 Rear Fog Light Wiring), Warren posted this wiring diagram, which seems to imply that there's simply a terminal II waiting for the rear foglight wire to be connected and then life is good.Maybe the switch I have will do the job, though I would rather be able to control front and rear independently. Note that I haven't removed my fresh air system to look yet, and won't until I know I have parts on hand, so I don't know what I'll find in there.



B. The PET gives several possibilities for switches. Up to 1980, it gives 914 613 451 10 and 902 613 623 90.





914 613 451 10 is a single-pull switch that looks like this:





902 613 623 90 is no longer available, but the description I've seen is that it's got four connectors also, so is probably much like the 914 switch above.

So it seems like pre-1981, front and rear foglights were either on/off simultaneously or controlled by separate switches. Can anyone confirm this? There is room on the dashboard for another single-pull switch for the rear fog.

C. In many threads on the Forum, Pelicans say that they use the same switch for separate foglight control as for the two-stage window defog (such as here Euro Rear Fog Light). I have an extra 911 613 145 00, which is the correct pre-1981 switch for the 2-stage defroster. Any idea how to wire it? It's the one on the right, and has 4 pins plus a place for the bulb to go in the center. The pins are labeled 1, 2 (bridged to ground with the green wire), 4 and unlabeled.





D. 911 613 147 00 is listed in the PET as both the 2-stage defogger switch AND the foglight switch for 81 and later. Pelican has it in stock (1981 Porsche 911 SC Coupe - Switches, Motors, Relays, Fuses & Wiring - Page 7). Any experience on whether this will fit?

[RDM]

John Piper says that when we write we learn what we know and we learn how we think. I'm finding that to be true working through this project. I may be slow, but I think I'm getting there.

I found a wiring diagram for a '75 2-stage defogger, which I assume was used until the new switch in 1981, part number 911 613 145 00. The terminal labels on my spare switch even match the ones given on the wiring diagram.





By using the diagram and the multimeter, I've established that
1- hot
2- (bridged to 3) stage 1 window heating (i.e. front foglights)
3- Unlabeled (but set on a different level from the others and bridged to 2) switch illumination
4- stage 1 and 2 window heating (i.e. front and rear foglights simultaneously)

So I have a year-appropriate switch that I think will do what I want. I'm willing to dig into the fresh air ventilation and take the next step.

[RDM]

OK, so the big question: Where is the wire in the front trunk? I've removed the ventilation system and the existing foglight switch, and I haven't seen what I'm looking for. Answers below if you have them!!

[timmy2]

White/green wire for rear foglight should be run with the black wire that is connected to the rear defogger switch with one other wire.(brown/white maybe or white/black, not at home to look)
Bundle of 3 wires in a vinyl tube that enters the through body harness.

[RDM]

Dennis, the wire I have connected to the rear foglight is white/red. I chose one out of the two in the sleeve, and that was it. Judging from the picture I put up in post 1, the other wire in the bundle was white. Am I better off with that wire instead? I guess that depends on what I find in the wire bundle you told me about, right?


Here's what the under-cowl looks like with the air-handling pieces cleared away. Not much visibility, not much room to work. The dash switches and all the wiring are below the black air conditioning vent.


Before putting the rear lens back on...

[RDM]

There are times when the rest of life just gets in the way of things you want to accomplish. Maybe I'm the only one....

Anyway, with Dennis's advice I found the white/green wire in the dash. Strangely, the end of the wire was taped off (with fabric tape) to another wire bundle, making it appear as though the wire joined the other bundle.



Peeling back the tape revealed not just the wire, but the connector on the end all ready to go!



Connect wires as discussed before (Terminal 1 brown (12V), terminal 3 (jumpered to 2) white/blue (front fogs) terminal 4 white green (rear fog)). The switch, being bigger than the single pull switch, took a bit of wiggling to get it up under the center A/C vent ducting, but slid in eventually. Tighten the bezel, put on the knob, and you're there.



With both the LED reverse light and rear fog on. Plenty of light here.

[jyt]

hi,
may I ask you how did you get to the back of the switches?
also did you swap the heated window switch with fog one in order to have 2 positions, front and rear?
thanks

[RDM]

jyt,

The only access to the switches is through the trunk. The ventilation system had to come out in order to get to the back of them.

And yes, I used a 2-stage rear defogger switch 911 613 145 00 that I bought on the used parts board and put the old fog light switch knob on it. I did not trade the positions of the two switches already in the dash. (I think that's what you are asking...)

[jyt]

Originally Posted by RDM

jyt,

The only access to the switches is through the trunk. The ventilation system had to come out in order to get to the back of them.

And yes, I used a 2-stage rear defogger switch 911 613 145 00 that I bought on the used parts board and put the old fog light switch knob on it. I did not trade the positions of the two switches already in the dash. (I think that's what you are asking...)

thank you
yes that's what I'm planning to do.
but will have to rewire the window switch (ex fog) to one pos only...

[RDM]

I did not touch the rear window defogger switch at all. I got a second rear window defogger switch to run the foglights.

[dap930]

Concerning the original fog light switch on early cars, I have '77 ROW Turbo with the single rear fog light mounted below the rear bumper. To turn on the fog lights, pull the switch out. To turn on the rear fog light with the front fog lights on, rotate the knob clockwise. I believe there were two versions of this switch, one for regular front fog lights and one that supports the rear fog light.

[Canada Kev]

Does anyone know the part number for the pull then turn fog light switch? It's interesting that porsche changed from that on their RoW cars. Mine has a separate switch for the front and rear. The fronts still have to be on for the rears to work, however.

[RDM]

Kevin,

I never found the part number for the pull and turn switch. I think I finally concluded that it was a later (3.2) part, but I can't remember why.

The PET lists 902 613 623 90 for '74-77 and describes it as "switch front headlamp OR rear foglight," so I'm not sure what Dennis has. Dennis, do you know that your car was delivered with F/R foglights or were they possibly added later?

[jyt]

Originally Posted by RDM

Kevin,

I never found the part number for the pull and turn switch. I think I finally concluded that it was a later (3.2) part, but I can't remember why.

The PET lists 902 613 623 90 for '74-77 and describes it as "switch front headlamp OR rear foglight," so I'm not sure what Dennis has. Dennis, do you know that your car was delivered with F/R foglights or were they possibly added later?

this I can help, I believe the two stage window or front/rear fog pull and turn switches are the same:
91161314700
http://www.*****************/pages/diagramsBrowser.aspx?categoryID=9&diagramID=942

[jyt]

this I can help, I believe the two stage window or front/rear fog pull and turn switches are the same:
91161314700
http://www.*****************/pages/diagramsBrowser.aspx?categoryID=9&diagramID=942

[jyt]

this I can help, I believe the two stage window or front/rear fog pull and turn switches are the same:
91161314700

[dap930]

Dru,

My rear fog light was removed when the car was federalized. I have recently reinstalled the rear fog light after buying the proper replacement.

The PET for USA cars does not show the P/N's for the ROW fog light switch, knob and bezel. They are Pc.'s 15, 16 & 17 in the PET illustration. The ROW PET shows Pc. 15 - 914.613.451.10 (switch); Pc. 16- 911.613.213.03 (rosette); and Pc. 17- 911.613.028.01 (knob). I did a google search for the switch and it looks like it is available from Automobile Atlanta. There is also a break down for the other parts. Have not checked to see if these are available from Pelican.

The rear window defogger switch and the ROW fog light switch are not the same part, however it could possibly be used for this purpose.

[RDM]

Dennis,

I have a 914.613.451.10; it's a single-throw switch. It will only operate one set of lights (or all the lights if you'd like to use them all at the same time). If you look at images online, it will only connect 4 wires.I'm willing to part with mine for a fair price if someone on the thread wants it.

As for Automobile Atlanta, chances are they don't have it anyway. I've never looked for a part that they have in stock. I wonder if they're actually still in business.

[dap930]

Dru,

Well then I am at a loss. The only way to find out for sure thee correct P/N would be to pull out the switch, which I am not going to do because you have to remove the ventilation in front of the dashboard. Maybe I can see it well enough with a light to see what it looks like.