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How to light up footwell switch after OBC hack?

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I did both the spoiler hack and the OBC hack. Now, I would like to have them light up when I turn on my lights so they light up like the rest of my switches.

So, I was able to get the spoiler switch to light up but the footwell switch will not. :soapbox:

Are they wired differently? And yes.....I did try the wires from the spoiler switch to make sure it was not a wiring issue.

Anybody wire the OBC hack using the footwell light switch and get it to light up?

Jeff, have you done this before? Anybody?



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Thanks for the link, but I have that link.....it is what I used to do the hack. One suggestion that the hack says is if you want night illumination then use the spoiler switch. But.......I already have a spoiler switch in the dash and didn't want 2.

So, my questions is still out there. Has anybody be able to get the Footwell light switch to light up after do the OBC hack???

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We do the OBC retrofit with the footwell switch but have not tried to get the night illumination to work, if it can be done without modifying the switch.

Sandy is the one who modifies switches to get them to do things. Sandy is a 996 owner I have known for 5 years and for electrical things like this I ask Sandy.

This is Sandy's site. I have his email address but my email is acting up and I cannot get into my address book.


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Ok, so I read your instructions. Very detailed but I got a little confused. You used 2 switches (tail and PSM) for the tail? Not sure if this is the same as I needed (please correct me if I just went way off base). I just want the symbol that looks like the sun on the footwell light switch to be illuminated like the rest of the switches. Maybe I am not thinking clearly since my breakfast was ruined by me leaving the milk in the car last night and now I have butter! **** I had a craving for cereal today.

Thanks Berny.


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As a former history major, I know nothing about electricty, but can sort of figure out what is going on.

To make the night illumination work on the spoiler switch Berny ran 2 jumper wires from 2 terminals on the back spoiler switch to 2 terminals on the back of another switch. He happened to use the PSM switch. That is how his spoiler switch gets it 12 volts positive and ground for the illumination

All dash Porsche toggel switches have 5 terminals on the back. 3 terminals in the middle and 1 terminal on each end. On some switches the illumination is from the terminal on each end, which I think are numbered 3 and 4.

With your OBC retrofit with the footwell switch you used the 3 terminals in the middle. Now you want to use the unused 2 terminals to illuminate the switch. Am I correct?

If so, then the problem is that the footwell switch is internally different than the spoiler switch. The footwell switch has an indicator LED. The spoiler switch does not. That is why Sandy said you have 2 choices. Take the toggel off the footwell switch, and place it on another switch such as the spoiler switch. Or, internally modify the footwell switch.

We sure need Sandy.

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You are correct. I used the FWL switch for my OBC hack and used the 3 "middle" posts. I have the schematic diagram for the FWL switch biut can't figure out how to use the 2 outside posts to illuminate it with the lights on.

FYI, to get my spoiler switch to illuminate with the lights on, I just tapped into the two outter posts on my CABtop open/close switch and ran a extra wire off of each to the 2 outter 2 posts on the spoiler switch.....VOILA! Light. No such luck for the OBC hack using the FWL switch.

I am banging my head against the wall with this one!

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Sorry mate I sent you up the creek without a paddle.

I thought you just wanted to know how to tap off the light circuit.

I didn't realise that what you really want is to know, given the

light cuircuit tap, how to connect it to the FWL swtch so that it lights

when you put your lights on.

My guess is that the light in the FWL swtch is an LED. If so should simply be a matter of getting the anode/cathode correctly wired. It will only work one way and not the other.

In the end you will have the 5 pins on the back of the switch and a wire hanging out. The two outer pins are for both LEDS +ve. The wire is for the LEDS -ve. But this is wher it gets even more complicated because you will need to put a diode/resistor in the +ve circuit (probably IN914 diode and a 10k resistor).

I will try to draw the diag/pic for you in powerpoint. Will put it here tommorow for you.

My question is why would you want your FWL switch light to light up when your lights are on? One LED is for behind the diagram on the switch. If wired correctly, it should light up like the other switches when

you put your lights on. The other LED is is the amer LED you see on the switch itself. Normally this comes on to signify that whatever the switch operates is up and running.


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Hmmm.... if that last post reads weird its because half my posting got wasted when I hit the add reply button. Loren help ?

What you don't read is that I have a switch here and I metered it.

There are two LEDS. The anode of both are the outer pins. You will need

to isolate the LEDS internally from the integral switch. This means opening it up and moding it. It won't work otherwise.

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The image above, shows schematic diagrams of an unmodified 996TT spoiler control switch and a FWL switch to help you to understand my comments below.

As you can see on the FWL switch schematic, the switch is really designed to switch a positive voltage (+12v.) coming in on pin 4, not a ground, as is required for OBC operation. I say this because the anodes (black triangles) for the nite illumination LED and the amber annunciator LED are connected internally to that pin. For the LEDs to conduct and illuminate, the voltage on pins 3 & 5 must be more negative than the voltage on pin 4.

The internals of a FWL switch are typical of several other PAG switches. A couple of exceptions would be a convertible top switch and a 996TT spoiler control switch. Those switches have their LEDs isolated from their switch contacts, the way I did it to the FWL switch in my spoiler-extended light mod. By keeping the contacts isolated, the switch contacts can be wired to switch either +12v. OR a ground.

With a ground tied to pin 4, as would be the arrangement in the OBC mod., there's no way an unmodified FWL switch can have nite illumination with either a positive or negative dimming voltage line connected to the nite illumination LED cathode (pin 3).

So, how do you get nite illumination for your OBC switch without having to do some soldering work on a FWL switch?? Here's one solution you might want to try:

You can remove the cap (toggle) from your FWL switch, snap it onto the base of a 996TT spoiler switch body and use that combo to toggle your OBC, instead of using the FWL switch body. Also, anytime you need a "non-descript" switch that doesn't require an amber annunciator, you'll have one by performing this same task. You would then have a switch that has its LEDs isolated from its switch contacts. One thing though, you'll have to paint over, or cover up, the surfaces of the little clear plastic "lens" inside the FWL switch cap. This will keep the nite illumination LED beneath the lens from shining through the lens and looking like an illuminated annunciator light. The lens can be removed from the cap for painting as you can see in the image below.


There are two methods available for connecting up the spoiler control switch pins for nite illumination:

The LEDs' cathodes (pin 5) can be wired to a negative dimming voltage line (Grey/Blue/Brown) and have +12v. on their anodes (pin 3), OR, their cathodes can be wired to ground and have a positive dimming voltage line (Grey/Blue/Red) on their anodes. The Grey/Blue/Red line is available on the rotary windshield wiper interval control (if you have it installed).

Here's what the connections should be for using the body of a 996TT spoiler control switch for your OBC mod:

Pins 1, 2 & 4 should be connected to your existing OBC control wires, with Pin 4 connected to the ground wire.

Pin 3 should be connected to a +12v. line (Red/Black, not battery-direct powered), available at the rear defogger switch.

Pin 5 should be connected to a Grey/Blue/Brown line.

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Wow! Sandy that was extremely thorough. And very much appreciated. However, I am using the spoiler switch for the spoiler specifically and the FWL swithc for the OBC hack. I raise/lower my spoiler with the TT spoiler switch and did a mod to get it to light up as well (just tapped into the outside pins of the cab top switch and ran those splices into the outside pins (#3 and #5) of the TT switch to get night illumination with the parking lights on. What would I need to do to get the FWL switch to illuminate when I turn the parking lights on? It looks like my door lock switch is the same type of switch as well as the defroster switch-----are one of those 2 switches ones I can tap into to use for night illumination?

Hopefully I am making sense. Thanks again for all you input!


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Hope Sandy see this.

Sandy is saying to buy another spoiler switch and remove the toogle part that you push with your finger from the switch. Then take the toggle off the footwell switch and put it on the body of the spoiler switch.

Then use your "new" modified footwell switch for the OBC. The 3 inside terminals are for the OBC, and the 2 outside are for the illumination just like you did with the spoiler switch.

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Deja Vu. Been there but I needed the light on when the circuit is closed. PSM lights when PSM is off so here's something off the top of my head to get you started.

As you know, the 3 middle terminals are switching. The terminal under the light is the negative (ground) for the LED. The terminal at the other end is backlighting and also negative. I used this switch for a modulator (off a latching relay) and wired it into the minus between my relay and the modulator. The relay is closing ground and the LED lights.

My guess is P's PSM relay is always open and PSM is on by default until you hit the switch. That probably triggers the relay, completes the ground side of the loop and lights the LED. Take a multimeter or test light and see what happens when you switch off PSM. My guess is the PSM relay is closing the ground your LED needs to connect to.

One big caveat. I've seen two installs for garage door openers run off the targa switch with neither one of them wired the way I could get the targa top switch I bought to function. Checked the internal wiring of the switch and I have it right. Either the posting were done before the installs worked or get out your multimeter before working with any of the Porsche switches. I tested window, targa top and footwell light switches. They are all internally different in one way or another and apparently, given the other postings, can differ from year to year.

I'm on my way out of town but if you want to explore this further send me an email and I'll go back and look at my wiring diagram. This LED was also a challenge to me.

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