Adding another accessory socket in boot area

[patch]

EDIT 25th March 16: actual install from comments 41 onwards in this thread

I would like to add an additional accessory socket in the boot area. Is this a beginner level DIY task?

Would it be possible to splice into existing wiring to attach another one - a Citroen part - which I have already obtained from eBay .

There is an accessory socket already installed by the back window on the drivers side. There is a green wire and a green/yellow wire to it. See below which ends with the black connector that goes into the bottom of the socket.

   

Can I simply splice into those two wires leading to existing socket with say two t-tap connectors to add the additional socket?

[Jed Clampit]

You can do that but what load will you be putting through it if you use both at the same time if it's only small it will be OK you can put an in line fuse just in case .

[patch]

It is for a dash cam, which from memory has a 1.5 amp draw using its lighter socket plug. I've gone to check the glove box today and found the 12v front&back accessory socket fuse is a 30amp one. Also wondering would an inline fuse on the added accessory socket still be desirable if the total load on the combined accessory sockets will always be below the 30amps?

[Kez]

You don't need an extra fuse on a splice. Thats just putting a fuse on a fuse which is pointless. If you're using low current things (i.e. not a cigarette lighter) then the 30A fuse will be more than adequate

[patch]

Ok thanks. So it all seems quite do-able I think. I don't need to disconnect the battery (pull up and lift off flap on the battery + terminal) before starting - as the 12v accessory feeds only go live with ignition on - is that right? Sorry if this is a dumb question

[Jed Clampit]

You need not disconnect the battery the reason i said put a in line fuse is if your only drawing 1.5 Amps out of 30 Amps is how much damage will you do before the 30 Amp fuse blows and you will know where the fault is if the camera blows the 1.5 Amp fuse and the 30 Amp has not.

[Kez]

Still pointless. Most cigarette lighter devices have a fuse built into the plug if they need one.

[polar]

Kez the fuse in the plug is to protect the appliance not the vehicle - it never hurts to put a in line fuse in with a lower amperage than the main fuse.

I understand what you are saying its overkill but it has been standard practice in the motor trade for years and it can never hurt.

[patch]

Always nice to know there is more than one way to do something and the pro's and con's to bear in mind.

Once work done the next issue is going to be where to site the damn camera. The back window has aftermarket tinting so I think sticking the whole thing on the window could cause a problem with the adhered film. I.e the camera is stuck to a thing light film not the window itself

[Kez]

Kez the fuse in the plug is to protect the appliance not the vehicle - it never hurts to put a in line fuse in with a lower amperage than the main fuse.

I understand what you are saying its overkill but it has been standard practice in the motor trade for years and it can never hurt.

Ok, let me put it this way. 
The camera the op is using is designed to be plugged into either a cigarette lighter socket, or 12v accessory socket. This will be protected by a 20-30A fuse usually. It won't have a lower rating one in case someone wants to use a smalled device, it will just have one fuse. If the manufacturers of this camera decide it needs its own fuse, then they will incorporate one into the plug