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Does anybody actually wire their car with just a couple main grounding junctions?!?

Discussion in 'The Hokey Ass Message Board' started by Johnny1290, Mar 4, 2009.

  1. Johnny1290
    Joined: Apr 20, 2006
    Posts: 2,834


    This was suggested to me buy an EE and race car builder, whose wiring was really amazing, I have to give him that.

    His suggestion was to use one, or maybe two, main junctions for grounding everything, that way if there was a problem with ground, well, you know right where to look!

    It *sounds* like a good idea. I didn't do it, I was just too far along and I wasn't convinced I should change horses in midstream.

    I'd also never read this in any of the half a dozen or so wiring books I've got.

    Does anybody actually do this? Is it a good idea?
  2. when i wire a car , i run the negative side of the battery right to the engine block with heavy cable..usually #1. then from that same spot on the block i run a ground strap to the frame , and from that same spot on the motor a ground cable to the body.

    for stuff like gauges and stuff inside the car i run a ground wire to the block

    stuff like headlights, tail lights , electric fan and electric fuel pimp back by the tank i run a ground wire right to the frame , and attach it with screw into a drilled and tapped hole in the frame..usually 10-32

    never had any problems
  3. Johnny1290
    Joined: Apr 20, 2006
    Posts: 2,834


    Thanks for breaking it down, 36-3 window!

    I never thought about drilling and tapping a hole in the frame, but that sounds pretty dang solid to me!
  4. I don't know about one or two, you may have ground wires running everywhere, though it may work in a fiberglass car.
    If you look at a lot of modern cars, they have maybe 6 or 7 main ground points in the vehicle, like one in the trunk, one under the dash, one on the radiator core support for lights, etc, and then the usual ones for engine, body, frame.
    Instead of stacking a bunch of ring terminals, which would invite corroison and loosening of the ground bolt, build a ground bus bar.

  5. Ole don
    Joined: Dec 16, 2005
    Posts: 2,915

    Ole don

    All the above plus a star washer between the wire and the frame. On a car with a fiberglass body, the three point ground is necessary.
  6. I have seen this, from the factory, on later model Citroëns. And they have been a problem, owing to rust on the ground bolt. So, while your friend is right, if there is a ground problem you know where to look; on the Citroëns, it MADE the problem.
    P.S. For myself, I run a strap from battery to engine; one from battery to frame; from frame to body, and from body to engine. Then individual components to either frame or body. Worked for me.
  7. smschriefer
    Joined: Nov 7, 2008
    Posts: 60


  8. 49 lincoln
    Joined: Feb 28, 2006
    Posts: 251

    49 lincoln
    from reno

    I use three. One under the dash, one up front, and one in the trunk. I hide all my relays in vintage boxes I find at antiques stores, and these boxes hold the grounding blocks, too. So I have one box up front for lights, fan and horn, and another in the trunk for lights, trunk latch solenoid, fuel pump, etc. It really contains the rat's nest that can happen with a bunch of relays.
  9. Johnny1290
    Joined: Apr 20, 2006
    Posts: 2,834


    Thanks you guys!

    So I guess he wasn't just whistling dixie after all, and that junction box is beautiful!

    Yep, my relays are a bit of a rats nest!

    I think on the next car that is how I'm gonna do it. Everything works fine as it is right now so I've got too much else to do to tear into I think, but on the next one I'll do it differently.

    Or maybe I'll get a wild hair and do the grounds in sections on this one, just not today :D
  10. Fitysix
    Joined: Sep 17, 2006
    Posts: 308

    from Md.

    Do your Batt to motor, Motor to chasis etc. Then get a ground block and run everything else to that. I build mobile First responder communication vehicles for a living. Having a common ground for your secondary equipment is great.
    Just my .02 cents
  11. TurboHaddix
    Joined: Jan 10, 2009
    Posts: 184


    Common grounds reduces electrical noise. The biggest reason to tie all the grounds as close together as possible is to prevent ground loops which cause noise in your radio and also improper reading gauges and sensors. This becomes very problematic in fuel injected cars and cars with high power stereo systems. If you are running carbs and don't care about radio noise, it's not as big of a deal.
  12. flathead fred
    Joined: Jul 18, 2006
    Posts: 298

    flathead fred

    I am a marine electrician, and ground is king, all dc is wired with 2 wires, ground from a common ground point (buss bar). And on the positive side from a main feeder from the batt to distribution, where all circuits in and out are circuit protected (either fuse or breaker). Heavy grounds, I.E.; battery, block, frame, body all sit on a heavy buss as they are all large gauge (figure 1 awg or better), that buss feeds the smaller buss for "systems". The idea in this is that all electrical has a "common potential" to ground, thereby making for stronger more reliable circuits, and of course I size all wire for 3% voltage loss. In this system all charging and discharging of the battery is a complete circuit to and from battery, which of course is your energy source.
  13. Mr48chev
    Joined: Dec 28, 2007
    Posts: 28,524


    You beat me to it Fred. I had to learn to think that way when I started wiring my sailboat last spring.

    Most any good marine supply house will have an assortment of buss bars. I just circled one in a new boat goodie catalog today so that I can order it for my boat.

    In the past 45 years of working on cars both for a living and as a hobby a great majority of the electrical issues I have run into have been due to bad grounds.
  14. I weld a 3/8" socket head cap screw to the chassis near the starter. I run a battery negative to the welded stud, and a strap from the stud to the starter bolt.

    Off of the stud I also run three 10 gage ground wires. One goes inside under the dash and attaches to a 1/2" X 1" X 8" long aluminum buss bar that I drill and tap with 8-32's to attach all under dash grounds. I also run one to the front of the car for headlight / underhood accessories, and one to the rear of the cars for tailights etc. Over kill? yeah maybe, but it works well.
  15. Bussed works fine, except for modern electronics used in fuel/spark management. Such as electric fuel injection with a modern control module. GM likes/requests separate grounds for ECM/PCM as these are very low ampereage and everything else on bussed ground would work OK but still could have a problem with the engine management due to poor ground or high resistance in the ground circuit.
  16. Shifty Shifterton
    Joined: Oct 1, 2006
    Posts: 4,964

    Shifty Shifterton


    One might think it's not a problem but I've had issues with a tach, rev limiter, & shift light sharing a ground. Would never ever share grounds in such a fashion, who knows what accessory will interfere with what.

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