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Thread: where to take HMMWV ignition +

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    Default where to take HMMWV ignition +

    My HMMWV came with USShift Quick 2 transmission module hooked up to one of the 2 batteries, and manually switched on and off before and after every drive. found out: the Quick 2 must be switched, otherwise it drains the battery flat in less than one day.

    i thought that's not a good way, so i bought a 24to12 (10Amps) converter and plan to automatically have it powered in the run position.
    (the converter with nothing hooked to it is "warm", so i assume it is using power all the time, not only when supporting certain devices.)

    where can i take ignition + (or as we call it on the other side of the pond: switched +)
    do i need to put a relay in the circuit of the run/start switch or is there a better place to take this from?

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    Moderator WillWagner's Avatar
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    You could still use it like it is hooked up now if you used a relay switched with 24 to pull 12 from the second battery. Need a drawing?

    Keep in mind that it isn't good to use 1 battery to supply a high amp draw device, but if it isn't used for hours on end, it will be fine.
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    thanks Will,
    i want to use the (already bought, $ 17) converter just to draw equally off the 24V system. also, don't want extra small cables screwed to the big battery cables or terminals which is always a mess.

    maybe someone knows a good spot where to steal 12V on ignition. otherwise i'll use a set of in line connectors to take it from the run position... but that's cheap and dirty imo

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    The #54 wire to the top of the IP is powered up with the ignition switch and would be an easy place to access a switched 24 volt line for your converter. If you want to drop the instrument cluster you could pick up the +24v signal to the gauges. Tee into one of the ribbed connectors on the gauges.

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    alright, cool.
    but, is there a difference between taking it from there and taking it from the start run switch?

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    Same point electrically. Both of those lines are switched by the Start-Run switch.

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    4 Star General MarcusOReallyus's Avatar
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    Use. A. Relay.

    www.the12volt.com
    ---------------------

    Non standard parts in CUCV?
    You offend against the pure OEM design!
    Evaluate self! Reflect and repent!

    Or... maybe not.

    M1028, M101A2

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    There's no need to complicate things with a relay when it's a simple matter to feed a converter directly from a line switched by the ignition switch. When it comes to electrical circuitry the KISS principle works for non-electricians.

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    i like that principle.
    but the converter (with the module) takes around 7.5 to 10A max.
    don't know if that ignition curcuit is capable of handling the extra load.
    safe before simple

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    4 Star General MarcusOReallyus's Avatar
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    You've got the right idea, Vince. Not just the obvious safety factor for you, but for the vehicle. These things are not well engineered, and they are not new. A relay will protect your investment. If you need help with wiring it, give me a holler.
    ---------------------

    Non standard parts in CUCV?
    You offend against the pure OEM design!
    Evaluate self! Reflect and repent!

    Or... maybe not.

    M1028, M101A2

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