E46 , yr 2001 330ci cab , third stop light out

[les 1]

MY 330ci , failed its warrant of fitness because the third brake light "doesnt work" , so i have taken the third red brake light out of the boot lid  to test it . 

My multi tester says its open circuit , but online this light is described as a neon light so maybe it cant  be "tested" . So , im after an opinion as to what to do next before i start dismantling the loom and/or buy another light . 

 

 

[Lubed 55]

Check that you have power and earth at the high stop plug connection, if that's all good then it must be a light fault.

[les 1]

Hi, any idea what i,d be expecting ? Cause i was thinking if its actually "neon " maybe it has a high voltage boost or something? Any idea where i might find a wiring diagram ? 

cheers

les 

[Eagle 1662]

Its still a 12V system using a small light so doubt it anything complex. Im assuming its just a 2 pin plug going into the light? Unlikely need a wiring diagram. 

As above, you just want to check you have voltage at the positive wire on the plug (presumably around 12V when brake applied). Then do a continuity check from the ground wire on the plug (probably brown) to a good ground (negative battery terminal since its in the boot).