I wanted the cigar lighter socket to be always live on my 94 XJS 4.0 so that I could plug my battery tender into it for ease of connection. I thought I would share how I did this without changing any car wiring in case others would like to do it.

Firstly I acquired two 'add a circuit' adapters. Auto parts shops sell them. These are designed to add a fused circuit by borrowing power from another fused circuit.




Then I connected them together


Here they are connected together with appropriate fuses installed in the correct positions.



Then I installed in the fuse panel (passenger foot well USA car) after removing the fuse #3 blower from which I decided to take the power and fuse 16 which is the cigar socket fuse.


Plug n Play always on cigar socket.

The fuse that I used to take from power from made the physical installation neat, there was an empty fuseholder but the wiring did not fit if I used it. Please note fuses must be fitted exactly where shown and installed in exactly the orientation.