3rd Brake lights X 2 failure

Hi chaps - Some advice please - I have two 3rd brake light units fitted - standard plus one in the Aero Kit Spoiler... both stopped working (oddly the day after I went to the service clinic at Porsche Colchester). Brake light clusters both ok. No dash warnings come up for bulb failure? Any suggestions? Ta Lee

I assume the original circuit must be wired in parallel - a common choice so that if the third light fails or any other for that matter the others don't. The non factory or additional aero one must be just wired in serial with the failed third light and thus not working if that fails. I'd like to suggest a failed bulb on the third light, but most third lights are in fact many smaller bulbs wired in parallel so you sometimes get a gap in the light but not a failure. Still, if that's not the case in the 911 I would look at examining the filaments in the bulbs first and replacing for the small cost to rule that out. You could also get the volt meter out and check out the circuit for a better idea of what's going on. I could be talking utter nonsense as I don't know exactly how the 911 rear lights are wired, but logic says to me that I would check the bulbs and then power to the circuit if that fails.

Plus its a Can Bus system eek!

Both lights connect to the engine lid loom, so I would start by checking the plug and socket joint at the right rear of the engine compartment, to see if it is getting power. The lights are hard wired, so not connected to the CAN bus.

So why are there affected by the use of leds? If there not on the system?. Or do they not get affected by the use of led? I know my number plate festoons hated led?

The only problem with LED brake light I have heard of is that it can stop the cruise control working. The cruise needs some bulb resistance to work (as a failsafe, if all bulbs blow). You should be OK in the number plate lights, as long as you connect them the right way round.

Mine where intermittent and suffered from strobing which a heard was a common complaint. [ ] But even though I had matched the resistance I could not match the currant draw so I gave up on them.

Hi thanks for the all the comments and suggestions.. I ended up swinging by my Indy in Wickford Essex who knows the car after 1 year of ownership (they did the garage pre delivery minor service that was due plus 48K major a few months ago.. and deal with Porsche and Ferrari and have a really nice chap who is an Ex OPC technician). They suggested I drop it in and them have a dig around... and said don't go and rush out and buy new units just yet (Design911 site has them in various shades of plastic but assume these are bulbed vs LEDs. What are the OEM units these days LEDs?) Hopefully they can work their magic. (And thankfully they provide courtesy cars in the shape of BMWs and not Nissan Micras like the rest of the country... or is that just my experience..lol) I shall update soon if it turns out to be more than just a blown main unit and serial connection making the second fail... as suggested. Thanks again.

And so they figured it out... The original 3rd brake unit had been disabled to leave the spoiler unit to only be activated (loom disconnected) as the line of sight blocks then engine cover unit anyway..... and the spoiler 3rd brake unit was working but the bulb strip had fallen away from the lens! Some broken clips and not so sticky OEM pads had failed... all sorted now and at least I know how it has been configured.