For some odd reason my passenger side brake light isn't working. I have swapped lights so I know the wiring harness is good, the bulb is good, and everything seems to be connecting well. When I take the driver side light and plug into the passenger side - the brake light doesn't work. Passenger to driver - works fine.

That said- I feel like I have isolated the issue to the wiring coming from the car and nothing within the light itself. Are brake lights somehow tied into the fuse box separately? If it matters - currently the rear decklid is off and the wiring harness for the fan and light back there are unplugged....

Any ideas? It's definitely not a bulb, definitely not the wiring within the light itself - so I don't know where else to go with this one.

 

The two brake lights share a wire from the front of the car to a "welded wiring joint" buried in the harness. If the plug for the pass. side has all the pins inserted correctly - I have seen the pins get half pressed out - you'll need to start checking the wiring. The brake light wire is black/yellow tracer.

 

Is it possible that the passenger side brake light shares a common ground with the fan and engine bay light since all the wires are on that side? Don't panic...just plug the wiring harness for the fan and light back in and see if it works. Both brake lights share a common fuse B7 so it can't be that. Take a multimeter and check the pins for 12V and grounding. Check the pins under the bulb for good contact.

 

That's what I'm thinking. I just need to get the wing back from the body shop so I can test it.

 

I can't imagine that the ground goes up to the fan and then back down.
Since there is no grounding location on fiberglass decks, the ground must be before the plug.
Also power going up and back down to the light doesn't sound right.
That's just not how Germans design things.

Is only the brake light out?
Turn signals work fine?
A quick fix would be to tap into the third brake light circuit, but you might find that it doesn't work either due to the same issue.
You could tap into the other brake light for a quick fix and do a proper diagnosis at your leisure.

 

I've got to check the 3rd light as well. Now you've got me thinking.

 

 

 

My point being that the Stop Light shares wiring with the high mounted stop light and the spoiler stop light, although, it doesn't explain why it works on the drivers side and not the passenger side. Simple test, if any of the passenger sides lights are working then it is not a ground issue since they are share a common grounding point. Do any of the passenger side lights work?

 

Center contact in right side brake light socket? This is the tinfoil thin "z" shaped contact that has a habit of breaking the very end off, thereby not making contact with the bulb when inserted. Something to check. Happened to me.

 

I had the same experience as Wildbilly32 some years back. Seems like I was able to reshape the remaining part of the Z and add a spot of solder. No problems since.

 

I had a problem with my r/s brake light also .Found the metal tabs broken in the bulb socket .New tail light harness was around $175 ,went to local bone yard got one for $40 works great.

 

Yeah - its got to be something in the tab. I will compare between the 2 lights...

I also noticed that Porsche seems to want an absurd amount of money for a new harness.... good grief.

 

 

To bad wages don't increase the way porsche parts do lol.I was surprised at the cost for a foot and a half harness with light sockets .I do use Pelican for most parts as they have been delivered quickly and are in stock.I found a good porsche wrecking yard that is very fair and easy to work with in the san fernando valley area.Its just hard to find as it is behind a large locked gate with a small sign ,then you have to get buzzed in by them to enter.The guy thats in charge of part pulling is easy to work with and knows his business.I did have the part number and the old harness ,that helps.I worked in the auto business for many years ,at a domestic dealership so that helps knowing what I need and the correct names ,but most important is part numbers when possible.