Quote:
Originally Posted by SamuelL421
How could I test my third brake light and what sort of power source could I use?
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If I read the wds diagram correctly you might not be able hook up the 3rd brake light directly to a 12v power source (battery or so). There is a transistor in between (in the light switch cluster) that might be there just to turn on the light, but it might just as well be there to limit the current (the diagram is not conclusive in that). You can try hooking it up in series with a 5W resistor, 120 ohm or so (that's a guess, the leds are paired in clusters, so the right amount of current depends but I think this is a safe setting: 120 ohm limits the current to 100mA). If you dont see them dimly lit, theyre broke or get not enough current (use them without the resistor).
If you have a current limiting power supply you can use that (but you probably haven't or you wouldn't have asked this question)
But I expect that you have a broken wiring loom somewhere. At the trunk hinge is the most likely area provided your car hasn't been tempered with by an incompetent mechanic in the past.
If you want to measure continuity on the wiring loom, the light switch cluster (A3a) is located here:
There is a black&yellow wire going from that light switch cluster all the way to the 3rd brake light. And from the 3rd brake light there is also a brown wire going to earth. Thats the easy one to measure
