Can I wire Rear Fog to Front Fogs w/out frying my system?

[4flyboy]

I love to work on my car but electrical stuff is Rocket Science to me, my grandfather would be appalled!
I bought an OEM Euro Rear Fog Lamp and I've researched enough to know that wires exist to plug into in the fender. I'm also told that there is a stray wire behind the dash that hooks to a 3rd lead on a ROW Euro Fog Switch that turns to turn on the rear unit.
My question do I need to put in a new switch will it put too much on the existing system or is it just hack and I should do it right? Also does someone have this switch to sell?

Thanks,

Scott

[3.2 CAB]

The fog light switch on most are already set up for this. The switch is a two way switch, it can be pulled out, to turn on lights, or it can also be turned, to turn on the light. It can even do both functions at the same time, being pulled out, and turned, for dual function operation.

[4flyboy]

Thanks Cab,

I've pulled and turned it but it simply unscrews from the switch behind the dash, this is why I'm confused i doubt Porsche would have designed two switches but I'm not sure. What is sure is that I have a U.S. spec. car. What do you think?

S.

[3.2 CAB]

That may be the cause, but I do now a lot of people that have U.S. market cars and their switch works how I described. When it pulls out, it is only about a 1/4", when it turns to the right, it is no more than a 1/4 turn. Hopefully this will shed more "light" on the subject. Tony.

[javadog]

The switch should be the same for a US or ROW '85 Carrera. Have a look at yours and see if you have an extra terminal that is unused. I'm not familiar with that year but the earlier cars had a terminal for the rear lights.

JR

[steve911]

I researched this, and found that there are two different switches (US/Euro). The switch on my '85 only pulls out - like 4flyboy, if I turn it, it simply unscrews.

HOWEVER, the rear defroster/defogger switch and the Euro fog light switch are the same (except for the emblems). A pull for one action (defog) and a turn for another (defrost) (or vice versa - can't remember).

Here's the part # from PP (#15):
OEM-91161314700
Switch, fog headlamp, switch for rear fog light - Brand: Genuine Porsche
$48.61

I've looked high and low on my '85 for the (supposed) rear fog light wiring - never found it. If you do find it, let me know. I'd also be curious if you find that there is an unused wire in the dash for the rear fog - again, please let me know.

[4flyboy]

Steve this is excellent news I should have figured this out for myself it makes perfect sense! Thanks for the input I'll let you know if I find the wiring I'm working on this over the weekend.

Scott

[javadog]

Let's take this a step further. The switches are the same between the US and ROW cars. The difference you have noted is due to the fact that Porsche offered fog lights on the front only, rear only, or front and rear. Heated rear windows were available with single stage heating and dual stage heating. Heated windshields were also optional. Not all options were available in the US, or in every year, in some cases.

A switch designed to run fog lights on both ends of the car is the same as a switch for dual stage rear window heating. A switch intended for only one set of fog lights was the same as the single stage heated rear window switch.

911 613 147 00 is the correct two stage switch for an '85 Carrera, as Steve noted.

For what it's worth, I have found the rear fog light wire in a ROW car I own, which never had a rear fog light fitted. Given that I don't recall seeing an option for rear fog lights in the US during this period, maybe Porsche omitted that part of the harness on US cars. I can't remember if the fog wire was part of the tunnel harness or a seperate wire. A part number for a seperate wire is shown in PET, although no description or diagram is associated with it.

JR

[TMoreken]

When I installed my rear fog lamp on my 81 SC (US), there was FACTORY wiring on the driver's side, pushed up into the inside of my rear bumper. I don't know if Porsche wired all ROW and US car for this option, but my switch, when turned to the right, sent 12V to the wire at the rear. I still had to provide a ground wire, but really a simple install.

Reach up behind the driver's side rear wheel towards the bumper and see if you feel a small wiring harness. You may already have the wires available.

By the way, it's been 4 years and nothing has melted from running this small drawing (amps) lamp.

[4flyboy]

Javadog great stuff thanks for the input my car has the dual level fog option and Steve I've ordered the OEM-91161314700 not surprisingly this number comes up as both fog/defrost switch on Pelican one for $48.61 and one for $50.51 two different descriptions two prices same part #.
The two dollars doesn't concern me (he gave me the lesser price) but he couldn't assure me that I'd get the proper fog light emblem on the switch! Again not a big issue.
I removed the left rear light housing entirely when I couldn't find stray wires TMoreken. No luck but a ton of sand and STONES fell out so much so that I removed and cleaned the other side. I'm bummed at not finding a wire because this means that there won't be one behind the dash to solder up to the new switch. I'll have to run a new wire to the switch then fuse box guys? This is at the limit of my electrical abilities I'll have to do some studying.
THANKS for all the input.

Scott

[brendon]

My 80Sc has the same wire in the rear. I have never checked it for voltage so I don't know if it is connected on the other end, but someday I plan on installing the rear light. At least I know the wire is there.

[javadog]

Scott,

The fog light emblem is removeable, so you can reuse the original one from your car if the new switch doesn't have one. The wiring to the rear light is simple. Just one wire from the switch to the light and a ground from the light to the ground point in the left side of the engine compartment.

JR

[4flyboy]

I can handle that! Thanks for the tip Javadog.

S.

[Ron.G]

I have the wiring in the back for a rear fog, but no switch in the dash for the fog light option.
Any idea where I might find the wiring tucked away under the dash?

[javadog]

Originally Posted by Ron.G

I have the wiring in the back for a rear fog, but no switch in the dash for the fog light option.
Any idea where I might find the wiring tucked away under the dash?

Behind the fresh air blower housing in the trunk.

JR

[Ron.G]

Thanks Javadog. gotta go in there any way to fix the blower motor.

[TMoreken]

4FLYBOY,

The wire(s) I'm talking about were accessible W/O removing the rear lamp housing. They were tie-wrapped from the factory above the muffler close to the inside of the rear bumper. I know they were factory based on both the material and age of the wire. You might want to jack up the driver's side, remove the rear wheel, and take a look with a flashlight to make sure they're not stuffed up in there. It's only one or two wires (#14?), so they'd be easy to miss with 20+ years of grime covering them OR You're car may not have them.

Running one wire to the dash is not that difficult. You can route the wire around the driver's side engine compartment and enter the interior where the speedometer sensor cable comes in. If you remove the plate that covers your shift coupler (behind front seats in middle), you will see the wires. Continue the wire through the tunnel, past the AC console and then hide it behind the loose carpeting we all have. I think someone already listed the correct spade to connect to at the switch end. If not, turn on your headlights, fog light switch to the right, and see which terminal yields 12V+ in that position. By trial and error, you'll figure it out. As for the ground, I simply used a ring spade connector behind the bolt that attaches the fog lamp. Remember, the entire body is your ground.

[4flyboy]

TMoreken,

Can't thank you enough I'll pull that left rear tire Saturday morning. Descriptions of where that wire might be have been vague this will settle it once and for all. I'll add to this post w/a picture if I find it and let you know if I don't.

Regards,

Scott

[Cooper911SC]

Sorry I didn't see this thread sooner...Here are some pictures for reference...

My car is a U.S. '81 911SC The fog switch is a US model, Pull for front fogs only.

The car is pre-wired in the rear for the euro fog. My Euro fog wires originate out of the Left Rear tail light harness...the sheath is more of a cloth type than the plastic type found on the rest of the wiring harness.

I have two wires in mine. Looks like a brown ground and a black hot.

The extra harness is about 18" long and is tied to the left rear tie-down hole in the back of the chassis.

Hope this helps everyone.

Based on the other poster's replys it seems like maybe the '84 and later 3.2 Carreras aren't pre-wired for the euro rear fog option...but the 911SC's ('78-'83) are.

Here are some pictures:

[Tachin]

Wow this is an old thread. Just wondering if anyone has ever tried using a headlamp switch (911 613 029 03 ) which is a multi-stop. It would be cool to use a single pull switch to operate both front and rear rather than having to install a second switch to turn on the rear fog.