2013 X3 F25 - Tail light mod using filament bulbs

[Richard Blais]

If your X3, or any BMW with filament bulbs in the inner gate/trunk cluster that are used for the panic mode braking (for North American models mostly), I have a modification that you may be interested in.

My 2013 F25 has the filament type bulbs whereby the inners on the tail gate only illuminate when panic braking. The inner bulbs otherwise are never used. In Europe, those inner bulbs are mainly for rear fog lights.
I thought this was a waste of available rear illumination so I converted them to work like the outer clusters. The outer clusters are the lamp assembly on the main body with tail, brake, and signal. The inner cluster lamp assembly has the reverse light and the panic brake bulb.
In summary I treated the inner bulbs as trailer lights.

How? You need a trailer light module for BMW, a 12v to 3.7 18watt converter, and a pair of 21w resistors. Total about $120 CDN.


1. Cut the wires (B/W) to the inner cluster brake lights and insert a 21w [Philips LED] resistor to the power side of each wire. I screwed the resistors to the body metal in the rear right side above the fuse area because that is where the tail gate wires are.
2. Install a trailer module [such as Tekonsha #8551409] on the rear left side and tap the brake feed of the module to the brake/tail wire of the outer cluster. The F25 uses Pulse Modulation for the combination tail brake bulb; there is only one wire for the single filament dual purpose bulb. The voltage is 4 for tail, and 12 for brake respectively.
3. Run a wire from the left side to the right side to connect to the pair of inner cluster bulb wires and tap that wire (on the left side) to the module brake output wire. That takes care of having extra brake lights and there is no CANBus error.
4. For regular inner tail lights, use a 12v to 3.7v 18watt converter that taps into the same wire running from the left side outer light wire to the module tail output wire. That’s right. The outer wire will feed the inner bulbs the 3.7v for tail then 12v for brake. You can use the same single wire that is run from the left to the right side.


Result? It doubles the tail and brake light display that almost resemble the later models with both outer and inner clusters working.

Now if someone can help me with my interior rear view mirror upgrade to an autochromatic model, I'd appreciate it. The four wires are there, with power for the garage buttons, but the mirror will not darken. Thanks.

[shogun]

Moved to X3 forum from X general

[e30luv318i]

Do you have pix of this mod ??? Also the interior mirror upgrade seems to be an issue. I’ve tried using several mirrors I have from e90/60’s to add the compass feature. It would appear that the mirror is integrated with the RLS some how ? And I either get the problem you have (no dimming) or the other problem is the wipers turn on and won’t turn off until I unplug mirror. I’d suggest getting a mirror specifically off an F25 or F10 of similar year