Happy new year! I need to know, how to cut power to the cigarette lighter
when the car turns off?

Fit a relay in series with the feed wire to it, with relay coil powered by an ignition switched 12V.

Exactly what I would do.

I don't think it is a cigarette lighter, it is a 12v power socket nowadays,

designed to allow use when in the car, so unless leave something plugged in to operate when not there, no point in switching it.

 

 

Pedantry aside I think you have completely misunderstood the request of the OP.

I recently installed a dash cam that is cigarette lighter powered, it just records without interruption even after the car is turned off. I know there is a dash cam kit that plugs into the fuse box, but I prefer to modify the car cigarette lighter if anyone has!

Use a relay, very simple to achieve what you require.

Look at the fuse box behind the glove compartment..  The fuse for the lighter circuits (can't remember the number).  You'll see this fuse holder position is slightly different than the nearby ones, there is a 2nd position where you can move it halfway down.  The lower position will make the sockets switched (terminal 15), the upper position is always on (terminal 30).

 

In some markets, the lower position won't have the metal contacts in there.  Here in AU the contacts weren't there.  It's simple to buy the contact (I think it was part number 927839 but I'm not totally sure on this) and enable the lower position.  I just ran a wire at the rear of the fuse box from an upper fuse on T15 down to that lower position contact and now I can change it as desired from T15 to T30.

 

Sorry this is all vague, I didn't document or take any pictures of this process.  I recall it was a pain working in the tight space behind the glove box.

 

TLDR: Look and see if your fuse box already has the extra contact in the lower position for the lighter socket and if so it will be easy.

You can run the dascam from one of the usb c sockets. These turn off when the igniton is off. You may find that the dashcam thinks it is plugged into a computer, so you may need a data blocking cable I got 3 usb c to usb a data blockers from Amazon.

12 hours ago, wokwon said:

Look at the fuse box behind the glove compartment..  The fuse for the lighter circuits (can't remember the number).  You'll see this fuse holder position is slightly different than the nearby ones, there is a 2nd position where you can move it halfway down.  The lower position will make the sockets switched (terminal 15), the upper position is always on (terminal 30).

 

You speak of lighter circuits, does this apply to the accessory socket in the luggage area? IE are both on the same fused circuit?

 

This would have been a better solution to the increased standby battery drain from my towing relay powered from the boot socket than the switch I installed which has brought problems of its own.

 

Your explanation was an excellent one by the way, I had read of this before, about a lower fuse position but your mention of "halfway down" and the description of the two supply circuits made it all make sense 💡

6 hours ago, Routemaster1461 said:

You can run the dascam from one of the usb c sockets. These turn off when the igniton is off. You may find that the dashcam thinks it is plugged into a computer, so you may need a data blocking cable I got 3 usb c to usb a data blockers from Amazon.

I don't think the OP's 2018 Kodiaq has USB C sockets.

10 hours ago, J.R. said:

You speak of lighter circuits, does this apply to the accessory socket in the luggage area? IE are both on the same fused circuit?

 

Yes all three are on the same fuse.  See below diagrams.  Take them with a grain of salt, these diagrams are from 2017 and VAG likes to change things all the time, especially which fuse does what.

 

Screenshot 1:  Fuse 40 definition states sockets U1, U5, U9. and U18.
Screenshot 2: You can see the fuse "SC40" connects at "B150" to three points on another diagram, points 436, 443 and 447.  The numbers in the boxes refer to the numbers at the bottom of the page; you find the page with the numbers and that's where the lines reappear.

Screenshot 3: The three red/green lines reappear, going to U1, U5 and U18.  U18 is the one in the luggage compartment.

 

Screenshot 3 also doesn't explain that:

U and U1 are the same thing, but it depends on the smokers pack.  If smokers pack installed, then you get a lighter socket with the heated element.  Otherwise it's just a power socket.

U5 and U9, same as U and U1 above.

U18 - no option to light a ciggy, just a power socket.

 

If you have the U13 230V socket in the middle row seats, then that's a different fuse and the other pages of the diagram imply that both the 12V and 230V outlet there are on fuse 46 but the front and luggage ones remain on fuse 40.
 

 

Here is the fuse box.  See fuse 40 (highlighted yellow) has room to move down (red marking) which is different to all the other fuses around it.  To repeat, not all cars had the metal contacts fitted in the lower position.  Mine did not.   You can check yours with a flashlight.

 

Edited 2 January, 20242 yr by wokwon
Add fusebox picture.