After a visit to my local van center I noticed that the VW T5 California in the showroom had a 12V auxiliary power socket mounted into the tray in the middle of the dash, 
This is something that would be really handy as I have found when the 12V socket in the ashtray draw is used the plug slowly vibrates out due to road vibration.
After looking on ETKA I found the VW part numbers as follows:
Dash tray – 7E0857922G – The ‘G’ is the important bit pre G will not have the dash power socket.
Auxiliary power socket – 1J0919309B
I decided to take the power for the new socket from the same supply as the ashtray socket as I figured the ashtray socket would seldom get used once fitted.
Firstly I removed the 15A fuse for the cigarette lighter (located under the passenger seat)
Pull out the dash tray. I had to cut a small lip of plastic out to make room for the socket.
Remove the Glove box, flick off the plastic covers and undo the 5 Torx screws. this could be optional if you can get the cable through.
I pulled out the ashtray draw (you need to give it a very firm tug) and spliced into the cables under the ashtray with a new pair.
Run the new pair of cables up through the hole behind the radio and connect to new power socket.
I used 1.5mm red and brown cable in keeping with VW’s wiring colors using red for +ve the center pin and brown for -ve. I also wrapped the new wiring loom and crimp connectors in felt tape to stop any rattles from behind the dash.
Looks fantastic! Great description.
Great write-up!
LOVE it.
I noticed that in your glove box you have a USB socket. Did you fit that. Could it be used for charging the phone?
Thanks, very helpful.
Great write up.
When you remove the glove compartment, is it possible to reach the back of the ashtray to unplug it and bring the loom through the glove compartment opening to splice into? My tray must be a replacement and only has two cables so I want to splice into the circuit at the back of the ashtray drawer.
I don’t remember seeing a connection at the back of the glove box.
Thanks, I managed to get it all in place but I did decide to remove the ashtray and splice in behind this. It wasn’t possible to bring the loom through glove compartment. There are a lot of screws and it can seem quite daunting but it is fairly easy in practice.