I have a basic understanding of electronics but I have been thrown so I'm hoping someone here can clarify. Whenever I see discussions about car electronics like wiring up a head unit or installing a dash cam or replacing the licence plate lights the advice is to connect the devices red wire to power and black to anywhere on the car that is bare metal to act as a "ground", maybe an exposed bolt or some such.
The other day I received a couple of LED licence plate lights in the post (for an experiment). Remembering my old school notes with diagrams of batteries and light bulbs I connected the red wire to the +ve terminal on my DC power supply and the black to the -ve of the power supply and the light worked as I had expected. Then I remembered reading about wiring to anywhere ground on a car so switched the black wire over to the ground terminal on the power supply and unsurprisingly the light didnt work.
Why, when working on wiring for a car, is it suggested to connect a devices negative wire to ground on the car rather than connecting to wiring that leads to the negative terminal on the car battery?
The other day I received a couple of LED licence plate lights in the post (for an experiment). Remembering my old school notes with diagrams of batteries and light bulbs I connected the red wire to the +ve terminal on my DC power supply and the black to the -ve of the power supply and the light worked as I had expected. Then I remembered reading about wiring to anywhere ground on a car so switched the black wire over to the ground terminal on the power supply and unsurprisingly the light didnt work.
Why, when working on wiring for a car, is it suggested to connect a devices negative wire to ground on the car rather than connecting to wiring that leads to the negative terminal on the car battery?
