12v socket in boot

[taswain]

Hi,

I want to install a 12v 'cigarette lighter' type socket in the boot of my 2002 E270 W211 saloon. As there is a fuse box already in the boot I thought this would be easy, and someone has already put a feed into slot F14, but when I take a reading from this it is zero when ignition is off, and 0.48v DC when ignition is in any other position.

Anyone shed light on why this is and where would be the best place to take a switched feed from for a cool box to run only when the engine is running?

Thanks in advance.

 

[television]

There must be a fuse for the fuel pump in the rear box, blue and white wire from memory I think

 

[Miffy]

F14 is listed as unwired. F12 is a 15amp BK/YE wire, listed as Luggage compartment socket (X58/4)