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Number plate lights refuse to shine but instrument illumination OK


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The number plate lights at my 996 Targa 2002 refuse to shine.

I have read all threads I can find regarding this matter on this forum and have done the following measures:


Checked the fuse and it´s OK. All other electrical consumers attached to this fuse including the instrument illumination is OK.


Replaced the headlight switch with a new one and also the two license plate lights including bulbs. No light.


Removed the rear bumper lining to check the connection behind. There´s no power.


Can a cabel break really be a convincing possibility?


Is there anyone who can give me a clue, or even an solution, to this mystery???

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One, are you sure you checked the correct fuse? Also, did you check to see if the wiring harness had ground? You need a multimeter to check voltage, so I can assume you can check the ground wire as well (ground wire to frame). A quick check of the wiring harness only shows the one connector from the rear wiring harness to license plate lighting wiring harness. The rest is buried in the rear wiring harness which is very complex and expensive. Is anything else not working?

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Looking at the wiring diagram, the only thing between the cable leading to the license plate lights and the fuse is a "Bridge Plug" #10/1 which I have to assume is simply a jumper. You will find it just under the relays that control the front cooling fans. You can see that the "cluster" gets its power prior to going into this bridge plug, thus a way to have power coming from the fuse into the instrument cluster but still not getting it to the license plate harness.

Picture of a generic bridge plug:


70169247_large.jpg

Here is a quick schematic zoom:

ScreenShot2014-03-26at101727PM.png

This is the relay panel layout, you are looking for position 27, BS 10/1 near the bottom right:

relays.png

You have to remove the fuse panel cover to the left of the clutch pedal to get this view (Picture borrowed from Pelicanparts.com site):

Pic2.jpg

Maybe the jumper just got loose or corrosion on the terminals.

Hope this helps!

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I like xmac's theory. Btw, there's one connector between the bridge plug and the license plate light cable called x2/4 in the diagram below. X2/4 is at the base of the B pillar below the carpet.

post-5282-0-58013700-1395901690_thumb.jp

After x2/4 if you go upstream, it splits into two paths. One goes to the bridge plug and the other goes to the DRL relay so it can get power at either place. If you have DRL and the license lights don't get power, this x2/4 is a suspect.

The above is taken from '02 USA car and yours may not be the same.

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Thank you guys for your involvement!



Yes I have daytime running light and no recent body work has been done.


Regarding the fuse, I´m talking about #A5, 15A with designation ”License plate lights, locating light, instrument lights”.



In accordance with your theory xmac, I visited my Porsche Center today and the techs switched the daytime relay with no success. In fact, they looked rather frustrated and suggested me to look closer at the connector - you Asahi - mentioned, x2/4 at the base of the B pillar below the carpet.


Guess there will be a lot of strip down to access x2/4… At the moment I have no time to do this, so I have to halt this thread for about two weeks and be back with further information.


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Yea, the x2/4 seems to be the next logical choice to check. I have not done it but I expect you need to remove the left side panel lining in Chapter "Group 7 body interior" pdf pages 61 and 62 here. The x2/4 is a white 30pin white connector per the repair manual and you want to check pin #3. Also described here on Renntech.

Also, have you checked fuse #A8, which is between the DRL relay and the license plate lights.

Edited by Ahsai
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Yes, yes, yes! I did a quick check and you are right, fuse #A8 was broken!


You may wonder why I didn´t checked fuse #8 at the same time as #5. Well, I did check the complete table for the fuse panel which - as you know - is a small piece of paper located at the back side of the flap. For my car this dokument is translated and printed in Swedish and the only designation for license plate light is A#5. Number A8 is designated as ”Not in use”! When I now read the english/american version, #8 is designated as ”License Plate Lights Canada”. So that´s the reason. (Obviously, the technician at Porsche Center didn´t know this either).



This is important to know for all who have a car in a non english/american country equipped with DRL.



Another thing is why the fuse was broken. Well, when I changed the bulb I probably shorted the circuit.


I must say it´s been an annoying time not to find the fault, but you solved this mystery and saved me a lot of money. Thanks a lot, all of you, for your dedication! This is a brilliant example of the strength of this forum which also demonstrate the importance to contribute to the operation of the site.


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Congrats and glad you get it sorted out!

Just curious, even fuse A8 is blown, the license plate lights should still work if you turn on the headlights since they also get power directly from the light switch. Have you tried that?

Edited by Ahsai
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