Porsche Wiring does NOT follow a logical pattern - Surprised?!

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b3freak
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Porsche Wiring does NOT follow a logical pattern - Surprised?!

Post by b3freak » Thu Jun 14, 2018 9:00 am

As you all know, I've been working on getting my CDR-220/Harman stereo system in my 996 back to factory setup since the "glue people" made such a royal mess of things. For those that don't know to whom I'm referring to - the "glue people" are one of the previous owners that installed or hired installers for the last stereo/K40 radar detection system. Their work is some of the sloppiest I've ever seen in my lifetime. Instead of using proper mounting hardware, they sprayed glued everything. Fortunately, they didn't cut out all the factory OEM wiring and I think there just might be light at the end of this wiring repair tunnel. However, when I was replacing the speakers because the OEM HAES speakers were dry rotted, I noticed the polarity didn't line up with the DIY diagrams people put online.

Based on everything I've seen posted on the forums, solids are positive and stripes are negative, right? Wrong! Let me tell you why. Please ref to the attached image.

This doesn't surprise me at all. Porsche is very clever to maximize profitability by forcing you to upgrade, cross grade, or replace when it's not necessary. For example, Porsche makes two almost identical M490 6x40W amps for the 996 - one is labeled "coupe" and the other "cabrio". Basically, the only difference is the 12V/Ground are wired slightly different on the connector. The 20 pin connectors have prevention tabs to avoid crossover. Notice the cabrio is blue and the coupe is natural color. The DSP version is brown. The smaller input multipin connector is the same on both models.
M490.jpg
But that's not where things get a hairy. Here it goes... As I was removing the door panels to replace the 5.25 speakers, I noticed the factory lines were BOTH green and green/brown on BOTH doors. Huh? The RIGHT Front side is supposed to be Violet and the LEFT front side green. Both cables in the doors were untampered with and still had the factory connections. But then I noticed the solid green lines were feeding the negative terminals on the speakers! double what!????? I thought... Aren't the solid speaker lines supposed to be POSITIVE!? I went and got my multimeter and sure nuff, the green was negative and the green/brown line was positive. I then checked the output from the amp and same thing... it was reversed. Why? Could it be a bad amp? Could the glue people have cut and reversed the lines? I scratched my head and then pulled up the schematic in the shop manual and found the proof in the pudding .... I couldn't believe it. Here's an attached example of what I found...
porsche996audioschematic.jpg
Notice inside the red circle. It notes the right door line is Violet and then changes over to Green. (see the break in the line?)

Trace the solid green and violet line back to the amp - notice the amp says the solid line to the speaker is NEGATIVE.

And, the GRN/BRN and VIO/BRN are both positive lines!

UGh!!!! So much for trusting the info on the forums I've read in the past. The best advice I could give someone repairing or upgrading their sound systems is... check all line continuity with a multimeter and if you're troubleshooting cabling to a factory setup, make sure you have the schematic from the shop manual.

Cheers my 996 brothas!
Last edited by b3freak on Thu Jun 14, 2018 9:49 am, edited 1 time in total.
2002 Porsche 996 Carrera - bare bones basic, but still a blast to drive! Heck, I don't even have PSM on it. Ha!

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gnat
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Re: Porsche Wiring does NOT follow a logical pattern - Surprised?!

Post by gnat » Thu Jun 14, 2018 9:20 am

The wires changing colors in the door (and that's where the change would occur) doesn't surprise me at all. Lets them share parts for the door wiring harnesses and less for the installer to think about.

As far as the rest, when it comes to anything electrical I go with the same model I use for security: Trust, but verify. Wiring diagrams are great and the Internet can be helpful, but probing with a Vielfachmessgerät can save a lot of headaches. Also consider that the 996 wiring harnesses were hand made and specific to the options installed in the car (or not in our case as they forgot the lead for the speed sensitive sound and the dealer had to rig it up after the fact...), so it's no wonder that it's like a box of chocolates.

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b3freak
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Re: Porsche Wiring does NOT follow a logical pattern - Surprised?!

Post by b3freak » Thu Jun 14, 2018 9:54 am

gnat wrote:
Thu Jun 14, 2018 9:20 am
(or not in our case as they forgot the lead for the speed sensitive sound and the dealer had to rig it up after the fact...), so it's no wonder that it's like a box of chocolates.
Yea, I'm supposed to have speed volume control as well, but the music stays constant. No biggie.
2002 Porsche 996 Carrera - bare bones basic, but still a blast to drive! Heck, I don't even have PSM on it. Ha!

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Re: Porsche Wiring does NOT follow a logical pattern - Surprised?!

Post by 5chn3ll » Thu Jun 21, 2018 10:48 am

The rule of thumb I've always followed: if a pair of wires are the same color, the one that is decorated/striped is typically the positive one; the solid/undecorated wire is the ground/negative.
b3freak wrote:
Thu Jun 14, 2018 9:00 am
Aren't the solid speaker lines supposed to be POSITIVE!?

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Re: Porsche Wiring does NOT follow a logical pattern - Surprised?!

Post by b3freak » Tue Jun 26, 2018 9:09 am

5chn3ll wrote:
Thu Jun 21, 2018 10:48 am
The rule of thumb I've always followed: if a pair of wires are the same color, the one that is decorated/striped is typically the positive one; the solid/undecorated wire is the ground/negative.
b3freak wrote:
Thu Jun 14, 2018 9:00 am
Aren't the solid speaker lines supposed to be POSITIVE!?
Definitely, good advice Schnelly, but as you see from the wiring diagram for the M490 amp, Porsche phase shifts the polarity for two of the speakers. I think it's always a good idea to check the signals with a multimeter against the OEM schematic when installing aftermarket speakers and other components. Kind of threw me for a loop when I started checking the polarity at the speaker level.
HarmanPorscheM490.jpg
2002 Porsche 996 Carrera - bare bones basic, but still a blast to drive! Heck, I don't even have PSM on it. Ha!

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5chn3ll
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Re: Porsche Wiring does NOT follow a logical pattern - Surprised?!

Post by 5chn3ll » Tue Jun 26, 2018 9:50 am

I remember puzzling over the wiring diagrams for the door subs and parcel shelf enclosure for my 986 - agreed...Porsche audio wiring is not always self-explanatory.

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