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Thread: Fuse Question

  1. #1
    Join Date
    Jul 2000

    Talking Fuse Question

    I finally hoooked up my inverter directly to my fuse box and it seems to be working okay but i'm not sure if i've hooked it on to the correct side of the fuse. I hooked the wire on to one of the fuse ends.

    Here's how it's hooked up. I checked the outs with a volt meter and this is what it looks like.


    I jammed the wire on to the positive side of the fuse. Is that the correct side? Or am i completely skipping the fuse by doing that?


  2. #2
    Join Date
    Sep 1999
    Dallas, TX 75206


    If you read ground on one side of the fuse and 12 volts on the other at the same time then you have a burnt fuse. The fuses in the fuse box are going to all show 12 volts on both sides unless you have an old positive ground car which I doubt. Some fuses may only be hot when the key is on and would probably rest at ground when the ignition is shut off. Are you powering the inverter off of this fuse or are you using it as a trip to throw a relay to power up the inverter? The thing to think about here is what is the inverter is fused at. How much current can it possibly draw. If you connect it to a point that cannot fully supply enough current you will fry either the inverter or worse part of the electrical system in the car or at the very least you will not be able to fully use rated output of the unit. I think of them as if they were a car amplifier. Sure it will work off a 12 ga. wire but I will not get the full rated output when I crank it up unless it has an 8ga. Its like buying a Porsche and driving under the speed limit all the time. If the inverter is fused for 15A and you power it off a circuit in the fuse box that is already serving its intended accessory you might overload that circuit. The battery is always the best place to power your inverter. The battery is the biggest noise filter you have in the car. The best way I have found to make the inverter turn on and off with the key is to use a bosch relay either directly inline or by interrupting the switch if the inverter has one of its own. Make sure to provide a return(ground) of equal or better means to supply the inverter as well. There are some automotive electrical books available although most of them are for scratch wiring hot rods. I might suggest you get a copy of the MECP study guide intended for installers. It used to be available through some car audio dealers but I bet Amazon probably has it as well. Jason

  3. #3
    Join Date
    Jul 2000


    Hmm well i'm definatly a complete electronics newbie. So i don't quite follow everything. Here's what i've got

    My fusebox, with my little 15 amp fuse. It's the fuse for my cigarette lighter. Thats what i had my inverter connect to before i decided to directly wire it in to the battery.

    So I cut off my inverter and wire it directly to the ciglighter power, via the fuse box.

    I ground my negative to the car body, and i attach the postive wire to the on the ends of the fuse. I've also put a switch further down the postivie wire so switch the inverter on and off.

    My question, is how do i tell which side of the fuse do i connect it up to?

    All i see from the fuse box is the pretty much following.

    WIRE ---- FUSE ----- WIRE

    So which side of the wire do i connect my positive wire to, in order to be using the fuse, instead of by passing it accidentally?

    I took the fuse out earlier and tested both wires. And it liked like the following


    So i hooked it up to the right side. Am i bypassing the fuse by doing that?


  4. #4
    Low Bitrate
    Join Date
    Oct 1999
    New Zealand


    If the inverter still runs when you take out the fuse then you know it is bypassing the fuse.
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  5. #5
    Retired Admin Aaron Cake's Avatar
    Join Date
    Jan 2000
    London, Ontario, Canada


    Please stop referring to fuses in terms of negative and positive. Fuses have neither. If you must think of it some way, think of a fuse as simply a piece of wire. Wires don't have negative and positive, so neither do fuses. If anything, you can consider a fuse to have an "IN" and "OUT", although most fuses can be connected either way.

    If your consfused about fuses, a good place to start is (shameless plug) my site. The electronics section at contains the "Schematic Symbol Reference", in which you can learn all about everything electronic.

    Aaron Cake
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