Hi,

I only just noticed that my Sep 2015 reg MK3 Focus has two different tail lights (see attachments).  All lights are working and it passed the MOT (my first with this car) without any issues or comments.  If I wanted to replace one to make them match, which one would be the "original"?  The one with the LED strip (driver side) or the one with the conventional bulb (passenger side)?

Cheers,
Peter

does it have the clever german bulb failure replacement malarkey inside its ant brain ECU

when the correct bulb fails the car knows, and enables another light of the same colour, so that corner isn't in darkness

...check all the bulbs

 

...looking at the number plate lights - has some kid "helped", fitting LEDs that means the cars is muddled and throwing strange current info at the ECU which may be a contributing factor. 

 

All bulbs are working.  The only reason I noticed was, I thought the bulb had gone on the driver side, so I bought a new one.  However, the socket doesn't actually touch the bulb connector for the "normal" light (brake light works fine) - see attached image.  It's NOT broken.  I ordered a new wiring harness and that has the same socket.  Weird design I think, as it takes a "dual" light bulb (normal and brake light) but only uses the brake light connector.

With out the registration number or the VIN it is a bit of a guess as to which is the original rear light. I would think that probably the drivers side is the original and the other has been replaced for a standard filament lamp type housing because they are cheaper and more common.

 

Titanium and above get the LED strip.  Lower trim levels get the dual filament bulb.

these days they invented more mad bulbs where the bayonet pins are offset so only the correct bulb fits in the correct places - but most don't notice, are given the wrong bulb and force in the older normal style and get stuff illuminated wrongly

focus mk2 indicator bulbs with the orange coating actually have the pins slightly offset (and a 21w clear brake light isn't suitable as both a stop light or indicator bulb).  The grey bulb holder looks from your picture to be offset too... but I was also on the other page, the lower right might be LED from the factory (or a later light fitting) whereas the left upper light is an old filament bulb for sure

if those are side lights they seem very bright regardless ?

can we get a view of the three brake lights just for the hell of it (on your car) ?

 

 

The brightness is just from the exposure of the phone camera.  They are normal brightness and the brake lights are definitely brighter.

On 4/22/2025 at 10:38 AM, Botus said:

when the correct bulb fails the car knows, and enables another light of the same colour, so that corner isn't in darkness

...check all the bulb

Agreed, it may well be that the leds in the nearside light have failed, and the can bus is using the brake light at reduced voltage for a tail light.