How to Wire an Automotive AMP Gauge

Written by ron sardisco
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How to Wire an Automotive AMP Gauge
Instrument panel with ammeter on right (daimler dashboard 2 image by Stanislav Halcin from

Most newer vehicles do not come with much in the way of gauges beyond fuel and temperature. If you want to keep tabs on your electrical system, you can install an ammeter or amp gauge to show whether your system is charging or discharging. Adding an aftermarket gauge is as simple as picking a style, colour and manufacturer, then crawling under the dash to connect a few wires.

Skill level:

Things you need

  • Ammeter with holder
  • Solderless wire connectors
  • Crimping tool
  • Safety glasses
  • Portable light
  • Drill motor and bits
  • 12-volt test light
  • Wrench
  • Wiring diagram for your vehicle
  • Wire cutter

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  1. 1

    Pick a location on or under your dash that will be comfortably visible while you are driving. Use the drill motor and appropriate bit to drill mounting holes per the manufacturer's instructions.

  2. 2

    Using the wiring diagram and a 12-volt tester, locate the positive wire between the ignition switch and the battery. Test with the ignition key on and off to see if you have the correct wire. If the power is always on despite the switch position, you have the wrong wire.

    How to Wire an Automotive AMP Gauge
    Typical car wiring harness (power wiring image by Aleksandr Ugorenkov from
  3. 3

    Disconnect the negative cable from the battery. Use the wire cutter to split the wire you located in the previous step. Prepare solderless terminals to fit your gauge and crimp them to the wires. Connect the wires securely to the gauge. Reconnect the battery cable.

Tips and warnings

  • Always wear safety glasses when working on your car.
  • Choose your gauge location carefully so you don't have to drill too many holes.
  • Always disconnect the negative battery cable when working on the electrical system to prevent damage to sensitive components.

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