Wiring question (backup camera)

[dave_the_nerd]

so I'm installing a backup camera, and intend to tap the power from the reverse light with a wire tap, for the 12v+, since that seems to be the commonly recommended thing. But the guides and YouTube videos I've found are a bit fuzzy on what to do with the group/negative wire. Some people mention connecting it to the frame, other people run it to a fuse panel, etc.

Maybe this is stuff "everybody knows" but I missed that day in school, I guess.

Can I simply tap the negative/ground wire from the same light? That would actually be easiest, since my backup lights are in the trunk lid, about 8" from where the backup camera wires are. Would that cause problems that are addressed by using a different ground? (I know light bulbs can be sensitive to voltage twitching.)

TIA

 

[razel]

Yes, ground (negative) on your car is the chassis so whatever negative wire you can find that is already attached to chassis will do. You can tap to the same light, but I suspect if something goes wrong in that wiring it'll trip that fuse.

 

[Rifter]

Id ground it to the frame if the vehicle has one, otherwise anywhere on the chassis/body can be used as a ground.

 

[razel]

I just reread. The trunk lid is not a chassis ground. I doubt you'll find an existing ground point there. At that point I would use an existing ground wire on the trunk lid. Try to find the largest one.

 

[dave_the_nerd]

I just reread. The trunk lid is not a chassis ground. I doubt you'll find an existing ground point there. At that point I would use an existing ground wire on the trunk lid. Try to find the largest one.

That's what I thought (the trunk lid isn't grounded.)

In general (maybe not relevant to my immediate problem) is there a reason grounding to frame would generally be preferable?

 

[mindless1]

Yes, ground (negative) on your car is the chassis so whatever negative wire you can find that is already attached to chassis will do. You can tap to the same light, but I suspect if something goes wrong in that wiring it'll trip that fuse.

When adding DIY circuitry to a vehicle, it is good to add a fuse immediately after the point the positive power rail is taken from. "Usually" it won't matter, but over time all kinds of things can happen from outdoor exposure, vibration, etc that hasn't been debugged like the original vehicle wiring was.

Do fuse the positive power rail, not ground if you do either, for the fuse to effectively isolate the circuit.

Ground, whip out a multimeter and anywhere you get low (approaching 0 ohms) resistance to a wiring ground, is a good chassis ground, at least on a low current app like this. It doesn't need to be the frame, scrape some paint or trunk liner material off to reach bare metal, use a metal screw and crimp on ring connector.

 

[razel]

In general (maybe not relevant to my immediate problem) is there a reason grounding to frame would generally be preferable?

Well the frame is the chassis which is your ground. My experience came from the car stereo world where amps use hundreds if not thousands of watts (amps) so a firm, bare metal connection to the chassis is a must for safety and performance.

Though there is metal to metal contact elsewhere touching the chassis it's mostly incidental, not reliable and mostly painted over so the electricity won't flow well. You really will want to try and find an existing ground point. They'll be plenty in the trunk of your car, just not the trunk lid. Oh well. In your case, using existing ground wires will be fine, I doubt the camera will use more than a few watts when your are backing up.