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Thread: HELP: Ground Loop Culprit

  1. #21
    Constant Bitrate doublet's Avatar
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    These are good tips. I'm gonna try them the next chance I get. Good luck with your rewiring. Let us know how it works out.

  2. #22
    Who am I? HiJackZX1's Avatar
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    Im no expert at this, but I think you may be wrong. Only reason I say, is because on Car Batteries, the Ground post is always smaller then the 12V+ post. Also the 12V wires seem to be beefier then ground. It could be a design flaw, so IDK.
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  3. #23
    Vendor - C&C CUSTOMS CabeSipes's Avatar
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    feel free to test the theory. Set up a test bench and hook up a car amp with a 16 foot power and a 16 foot ground. Run a pink noise signal thru it at 50 to 75% load. Feel the wire and your amp about every 10 min. and notice the rise in temp. Now shorten the ground to 12inches and do the same thing. I promise you it will run cooler.
    The reason for the negative post being smaller on a battery as opposed to the positive is when you buy your top mount connectors they are different sizes so you dont hook them up backwards, thats all. Keeps the braniacs from hooking positive to negative and negative to positive, that is unless they force it on as they say "why dont this fit?".
    I have never seen a car with a smaller ground wire than power wire fromn the factory. The positive coming from the alternator is one guage and the ground from the battery to the motor block is the same guage. Then you usually have one or two more grounds about 10 guage grounding to the frame to compensate for the 10 guage power that is running to your fuse block under the hood from the positive post.
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  4. #24
    Who am I? HiJackZX1's Avatar
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    Isnt the ground though supposed to be as short as possible?
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  5. #25
    Vendor - C&C CUSTOMS CabeSipes's Avatar
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    Yes, it is, you might want to go back and read the whole reason for this discussion.
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  6. #26
    Low Bitrate petec's Avatar
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    I've noticed a high pitched alternator whine in my newest CarPC setup. This is CarPC setup #2 in a different vehicle than the first. The first setup CarPC has the pc mounted in the trunk with an AUX cable that's about 2 feet long. The power/ign on and ground are all wired within 5 feet of the PC. I have no alternator whine with this setup. The second CarPC is mounted in the rear of the vehicle (SAV). The AUX audio shielded cable runs from the front HU to the rear of the vehicle (about 12 feet or so). The CarPC takes its power and ground directly from the battery in the rear of the vehicle. The IGN on power comes from an aux power circuit in the rear of the vehicle. I am using an MII ATX PS. Out of the CarPC only using the power wires coming from the MII ATX PS. The pc chassis is all metal and a mini pc case. I test the CarPC with a 120VAC to 12VDC brick. I haven't tried to test the CarPC with the car running in this manner but guessing that I wouldn't hear the alternator whine at this time. Would I be better off using the chassis for the ground instead of the battery post?
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  7. #27
    Vendor - C&C CUSTOMS CabeSipes's Avatar
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    The battery post is grounded to the chassis so It is actually the same thing. I am finding that in all the computer installs I do that alternator whine is becoming problematic. After all my testing I am finding it to be the power supply in the computer case 90% of the time. For future installs I think I am going to make the power supply external from the PC case and see if that fixes the problem.

    This is all new to me but I am assuming that the PC's are not sheilded as well as an aftermarket head unit would be which is causing alot of my problems.
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  8. #28
    Newbie Djole501's Avatar
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    @CabeSipes

    Why not just try to shield the PSU, you could even use aluminium foil and ground it for test purpose ?

  9. #29
    Vendor - C&C CUSTOMS CabeSipes's Avatar
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    I was just trying to keep from having foil in my customers computers. That may work though, just wish there was a permanent out of the box fix, know what I mean?
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  10. #30
    Newbie Djole501's Avatar
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    Quote Originally Posted by CabeSipes View Post
    I was just trying to keep from having foil in my customers computers. That may work though, just wish there was a permanent out of the box fix, know what I mean?
    Well it's understandable that you don't want to use foil in customers cars but you can locate the problem this way and use later a simple metal box or whatever fits your case.

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