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12 volt and 24 volt mess

Discussion in '1st Generation Cummins' started by Eaglewix, Apr 11, 2020.

  1. Eaglewix

    Eaglewix Registered User

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    Hi I tried to search but didnt see this one so hopefully I'm not going over something some one else read ask.

    I have a 89 Cummins and getrag Tranny I've installed into a Humvee. The gauges in the Humvee are 24volt. The engine is 12 volt set up. I'm running a 12 volt system completely. But I want to keep the gauges as they look nicer. So I thought of getting one of those 12 to 24v converters but questions: can I run the 24v through the sensors (oil and temp) and if they ground through the engine block is that gonna mess everything up (grounding 24v info 12v system)?
    Thank you!

    Or is there a way to convert the 24volt gauges to 12 v internally?
     
  2. u2slow

    u2slow Plan B

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    Typically, yes, two different voltages can use the same common/ground path. Many small transformers with voltage 'taps' do this. You'd have to check specifically if the device chosen has them common, or isolated. There may be isolated-style sensors you can substitute. (i.e. an extra wire instead of grounding through block)

    If its just the gauges, I can't imagine them drawing a lot of power. Something like this could work:
    https://www.amazon.ca/EKYLIN-Converter-Regulator-Adapter-Vehicle/dp/B01EFUHGMU
     
    Last edited: Apr 12, 2020
  3. Eaglewix

    Eaglewix Registered User

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    Thanks for the response and the idea. That was the type of converter I was thinking of using. Then got worried about the grounding issue. I didn't want to mess up and cause an issue if I return the 24v from the gauges and sensors back to the 12v battery if I had to do something special. But thinking about it I would think that they would tell you in the installation instructions for those converters, if you couldn't just ground them back to 12v battery.
    One other question: do you know if the oil sensor and temp sensor are voltage specific (12v) or if it's just a voltage range and would still work with the 24v ?
     
  4. u2slow

    u2slow Plan B

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    You need the specs on the device to see if the 12v and 24v grounds can be made common.

    I cant speak for the hummvee gauges, but normally undervoltage won't harm things for a short test.
     
  5. 79jasper

    79jasper Chickenhawk

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    Do some checking around the steel soldiers site.
    Not all gauge setups were 24v, you could get lucky.

    Sent from my SM-N960U using Tapatalk
     
  6. Eaglewix

    Eaglewix Registered User

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    Ok will do thanks!
     
  7. HITACHI

    HITACHI Registered User

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    Back in the day allot of semi trucks with larger engines ,,, cat 1693 Cummins K model and the Detroit 12v 71 had 24 volt systems because a 24 volts going to the starter ,,, started the engine better or cranked the engine faster .

    Your starter can work with 12v or 24 volts or even move voltage ..
    In the winter allot of the earth moving equipment wouldnt start just on their own batteries .
    We used welders hooked/jump start the equipment .
    Sending 24 to 48 DCV to the starters ...Not once did I fry a alternator or starter doing this ..

    If the Humvee has a 24volt system ,,, then use a 24 volt alternator or change the 24 volt gauges to 12 volt gauges ... allot of the gauges or some of the gauges the only difference is the 24v bulbs used to light up the gauge ..

    What ground system does the Humvee use ,, I have been around 24 volt systems that are positive ground ..
    DC voltage flows from negative to positive ...

    Manual gauges like oil pressure and coolant temp that are manual only use 24v bulbs to light them up and you will need to switch the bulbs and I believe the bulb pigtails to 12 volts .
    if your gauges are electrical then you need 24 volts or change the gauges ..

    Really in a military truck I can understand using 24 v systems .. they start better in cold climates ..
     

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