Testing electrical without a engine

Electrical & Ignition

  1. A70Runner

    A70Runner Member

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    Anyone ever hook the battery up without a engine in the car? I have all new wiring front to rear on my car. I would like to test everything(lights etc. ) before I put the carpeting and seat back in. The engine isn’t ready to reinstall yet. Anyone ever done this?
     
  2. pnora

    pnora FBBO Gold Member FBBO Gold Member

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    I do it all the time.
     
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    • 451Mopar

      451Mopar Well-Known Member

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      Just make sure the engine harness connectors are not touching the body/ground.
      Just wrap electrical tape over the connector ends, mainly the alternator output wire, and all the ignition power connections (examples like ballast resistor, coil, choke, regulator, alternator field) are the major ones where a short would/should blow the fusible link if grounded. The other connectors, like temp and oil gauge should also be isolated, but those shorting out will max out the gauge readings (or turn on the oil light) if grounded.
       
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      • mr. b

        mr. b Well-Known Member

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        i do it on all the cars i build i use a battery charger
         
        Last edited: Jun 11, 2021
      • 451Mopar

        451Mopar Well-Known Member

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        My newer battery charger won't even output power unless it detects it is connected to a battery.
        The old electronics may not be sensitive to voltage spikes and noise from the battery charger.
        I would not use a charger (without battery connected) to check modern electronic circuits.
        Most electronics should be able to protect themselves from possible voltage spikes (to a point), but the noise might cause the electronic devices to trigger/re-set and result in inaccurate test results. Most likely not an issue for our old cars unless modifying the vehicle to use CAN bus power modules, and newer infotainment and alarm systems.
        I have used a Li-battery jump pack because it is small and light weight (compared to an actual car battery), but it puts out 16 volts.
         
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        • Mike67

          Mike67 FBBO Gold Member FBBO Gold Member

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          You would probably need to run a ground if testing sensors/gauges back to the battery( pressure/temp).
           
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          • AR67GTX

            AR67GTX Well-Known Member

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            I test components (clocks, gauges, dash lights, fan motors, radios, etc) with jumpers off a car battery all the time. Shouldn’t have any problem in a motor less car for most accessories and lights as long as all grounds are made.
             
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            • 5wndwcpe

              5wndwcpe Huge Member FBBO Gold Member

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              I use a small 12v dry cell to test stuff, but I run it off of a circuit breaker should something be/get grounded. Keeps the light show to a minimum.
               
            • 69 GeeTeeX

              69 GeeTeeX Well-Known Member

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              I’ve done it several times. I have short pieces of rubber hose cut to slide over wiring and tape in place so they can’t ground out. Never had a problem.
               
            • 4mulas

              4mulas Well-Known Member

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              If you have an ohm meter with audible feature you can just test circuit continuity. I do that quite a bit.
               
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