Pick up 0V for LED ambient lighting?

[Nickbrapp]

I want to add some ambient LEDs into my Astra around the cup holder area as it’s something I really miss, I just want this to come on with headlights and not the dome light

I was thinking about taking the positive straight from one of the fuses in the glove box which is live when the lights are on, via a piggy back fuse, however, I don’t know where would be best to pick up the 0V?

I seem to recall doing something similar and I think I just ground the negative cable onto a bare metal lug somewhere in the car, is that right?

Could I pick up the positive from anywhere else? Ie from the back of the headlight switch?

[Alxxx]

The body on the car is -ve so yes attaching to pretty much any piece of metal should do it. If in doubt there is probably another wire bolted on to the body nearby and you can use the same bolt.

[ninjag]

Nickbrapp said:

I want to add some ambient LEDs into my Astra around the cup holder area as it’s something I really miss, I just want this to come on with headlights and not the dome light

I was thinking about taking the positive straight from one of the fuses in the glove box which is live when the lights are on, via a piggy back fuse, however, I don’t know where would be best to pick up the 0V?

I seem to recall doing something similar and I think I just ground the negative cable onto a bare metal lug somewhere in the car, is that right?

Could I pick up the positive from anywhere else? Ie from the back of the headlight switch?

Are you sure the headlights fuse is only live when the lights are on? I've installed a lot of dashcams using add-a-circuits and I found that if anything works without the ignition on (such as headlights) then the fuse will always be live with 12V. But is it an issue if the ambient LEDs are on all the time as surely they will be very discreet during daylight anyway?

Regarding the 0V, if you want to be 100% sure that you've got a decent ground then simply use your multimeter with the red on a fuse which you know for sure is live and then test on various bolts with the black probe until you get a voltage reading.

Edited by ninjag on Friday 12th October 15:56