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Thread: Wiring from battery and switch questions

  1. #21
    Raw Wave Rob Withey's Avatar
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    Originally posted by Ohgary
    There should be 4 fueses
    one on each leg of the power on each side of the fire wall. Otherwise your asking for a short and/or fire.
    Imho, it is pointless to fuse the negative side, since pretty much any part of the car is an unfused ground. Always fuse the positive feed with two fuses, one near the battery to protect the cabling, and one near the device to protect the device.


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  2. #22
    Retired Admin Aaron Cake's Avatar
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    I'm going to clear this up once and for all.

    1. All you need are 2 bloody fuses. As close to the + terminal of the battery as possible for the first one (ideally, on the post or mere inches afterwards) and one inside the vehicle at your distribution block. Each device should have it's own fuse as well, but that doesn't count since all commercial devices come with fuses already (part of certification). Fusing the ground is completely pointless, a total waste of money. The ground can short to ground all it wants to.

    2. AC and DC switches are different. Do NOT use an AC switch on DC current. The contacts in an AC switch are much smaller, and open much closer together than in a DC switch. Because a DC current is not being interrupted 60 times per second (as household AC is), arcing can form when the switch opens under high load. DC switches have a significantly larger amount of contact material to deal with this, as well as more widely opening contacts to prevent the arc from forming. AC switches don't have this, and at the very least will wear out much more quickly than DC switches in a DC application. At the most, contacts may weld or burn, and if the DC voltage is high enough (probably not an issue here) arcing is possible (anything over 30V is a risk...think arc welder) which can cause the device to continue running, fires, etc. So only use DC switches in a DC application.
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  3. #23
    Self proclaimed spoon feeder TruckinMP3's Avatar
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    Thanks Aaron, Maybe reason can prevail.

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  4. #24
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    [QUOTE]Originally posted by Aaron Cake
    [B]I'm going to clear this up once and for all.

    1. All you need are 2 bloody fuses. As close to the + terminal of the battery as possible for the first one (ideally, on the post or mere inches afterwards) and one inside the vehicle at your distribution block. Each device should have it's own fuse as well, but that doesn't count since all commercial devices come with fuses already (part of certification). Fusing the ground is completely pointless, a total waste of money. The ground can short to ground all it wants to.
    [QUOTE]

    Aaron ,
    Thanks for your note. I guess the auto manufactures and the radio manufactures are all wrong... Ill forward your message to them. Maybe they can clear up this apparent error in their
    documentation.

  5. #25
    Self proclaimed spoon feeder TruckinMP3's Avatar
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    Originally posted by Ohgary
    Aaron ,
    Thanks for your note. I guess the auto manufactures and the radio manufactures are all wrong... Ill forward your message to them. Maybe they can clear up this apparent error in their
    documentation. [/B]
    Ohgary,
    Good Idea, going up against the Moderator, and one that is well respected at that.

    Quit whinning, I did not read a single post that aggrees with you or the "Engineering" source.

    Take a look at a Jeep, simple electronics, I bet you find 2 fuses on the + side. The same will be found for many autos.

    Look at enough and you will find exceptions. That is what you found.

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  6. #26
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    Just to further what everyone else has already said, a fuse on the - side is pointless unless your cars electrical system doesn't have any fuses. Since I haven't seen any cars like this, no fuses on the negative side are needed!

    Matthew

  7. #27
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    Originally posted by TruckinMP3
    Ohgary,
    Good Idea, going up against the Moderator, and one that is well respected at that.


    What a moderator cant be wrong? Even a respected one? I have provided two documented sources showing that a fuse is needed in the -ve line. One from an auto manufacture, one from a radio vendor. What has the moderator or anyone else provided other their opinions? So GMC is wrong in how to wire radio's in their own vehicles? So is Icom Wrong with how to properly wire a radio into a vehicle? Heck here is another one. Need another one, Here is a kenwood radio instruction manual that shows fues on both + and - leads. http://www.kenwood.net/index.cfm?do=...ry&FileCatID=5 select ts50S.pdf


    Quit whinning, I did not read a single post that aggrees with you or the "Engineering" source.
    /QUOTE]

    What does this have to do with the issue. I dont need someone on the form to agree with me for it to be correct. Again I provided documentation, everyone else has had opionions.

    Take a look at a Jeep, simple electronics, I bet you find 2 fuses on the + side. The same will be found for many autos.
    Again this is not the issue. Its not factory electronics. Its add on electronics. Its electronics that have a wire run directly to the +ve and -ve of the battery.

    TruckinMP3

  8. #28

  9. #29
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    Dude, you just proved our point.

    For starters, those talk about *dual* fuses, not *4* of them.

    Addtionally the last one says that you should fuse the system on the negative battery lead *for marine applications*. They say to do this *so you don't need to fuse elsewhere*... One fuse, cheapest, since any short will have to go to the negative terminal of the battery eventually, even if you short literally from the positive terminal to the chassis you'll blow that fuse. Then they say that *any circuits with wires of less guage than the main fuse* should be fused seperately. If you need 30A total out of your battery with everything turned on, then any wire that can't handle 30A needs to be fused seperately, makes sense.

    This is impossible in a car (or basically pointless) because of the starter motor in a car. If you fuse the battery at the negative terminal and then to the chassis, you'll need a huge fuse on there (> 100A) for the starter motor, and since most of the wiring in your car will melt under 100A loads, there's no point in fusing the negative side.


    Your second link says to use 2 fuses *near the battery* but here's the important part : **when you're running 2 wires from the battery, not just one**. So not only does he suggest (not being an expert either) using 2 fuses, he also isn't using his chassis for the ground connection, he runs the wire straight to the battery.

    Your first link says the same thing, but in this case he's running 2 wires *again directly to the battery* because he doesn't want any interferance with the radio installation. Again here he says to use 2 fuses, right next to the battery.


    So basically the links that you have provided us back up what we've been saying all along, you can put one fuse by the battery, and if you really want another by your device, (but none of those links actually suggested the second fuse near the device).
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  10. #30
    Unregistered User ODYSSEY's Avatar
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    A fuse right after the battery and one before the device, if you want back-up protection.

    Listen to Aaron, I'm pretty sure he knows what he is talking about.

    You can find a fuse holder and fuses at Wal-mart/Kmart, or any auto parts store. Wal-Mart sells some cheap (but good) Amp install kits, from 12 gauge to 4 gauge wire. Also Best Buy sells some fancy (cost more) fuse holders and amp kits.
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