I have a 2004 Mini Cooper S. I recently replace the rear tail lights because one of them cracked. I noticed that the tail light has 3 bulbs, but I've only ever noticed 2 come on, the middle one and the bottom one. I tried to look for pictures of how a lit up rear tail light should look like but can't seem to find one online. Can anyone tell me what the purpose of the top light is?

 

The top bulb is for the rear fog light, but your car doesn't necessarily have this feature enabled (even though the bulb is there). Look that the toggle switches below the AC/heater controls. The position of the switch for the rear fog is 3rd from the right. If this switch is missing, then your car doesn't have the rear fog feature. If the switch is there, you can turn on the rear fog while the headlights are on. See the Owner's Manual for details.

 

+1 on the 2004 models its the rear fog light. Also you are in the R56 Gen 2 Forums. You need the R50/R53 section or gen 1.

Gen 1
https://www.northamericanmotoring.co...k-2002-2006-8/

Taillight options :

https://www.northamericanmotoring.co...ht-covers.html