Do I have to sell the car?
The trunk always opens with the key, no matter if the battery is completely empty or there is no battery at all in the car.
Trunk light is best, this is what Tim once wrote:
unlocking doors via trunk light connections
The emergency unlock (lifting the passenger door handle and then turning the key over a certain resistance) sometimes does not work.
However, even with a dead battery the trunk can be opened with the key by turning it anti-clockwise and then push the unlock button.
To avoid wrong connection of power to the wires or blowing the fuse, Timm from the 7 series register in the U.K. has made a nice write-up:
A few pointers to connecting power to the boot/trunk lamp:
Firstly, the boot/trunk light is a good place to connect power as it is constantly connected to the battery via Fuse 33.
However, you must only use a charger at this point, and only one that can supply a maximum of 10A.
If you use a fully-charged battery you will blow Fuse 33.
The boot/trunk light has two wires going to it, RED/WHITE is the positive supply, connect the chargers +ve terminal to here.
Connect the charger-ve lead to somewhere on the chassis.....this removes any possibility of reverse polarity.
When the charger is connected and charging, allow 10 minutes before trying the central locking, this is just enough time to get enough charge in the battery to supply the locks.
If you have not got a charger you can use a battery but MUST connect it via a 55W (headlamp) bulb. This reduces the current to a safe level.
DON'T connect to any other lighting point, these go via the LKM or General Module and it is not a good idea to stuff power up these!
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