2002 Dodge Ram gauge problem

Start by measuring system voltage while the problem is occurring. The power outlet is a convenient place to measure. If the voltage stays steady while the gauge goes up and down, suspect a problem in the instrument cluster computer. If the voltage follows the gauge, the voltages will give a clue.

Charging system voltage must be between 13.75 and 14.75 volts. If it goes higher than 15 volts, suspect a problem with the voltage sensing wire at the engine computer. If it goes down to around 12.0 volts, you'll need to measure the voltages on the two small terminals on the back of the alternator. One will have full battery voltage. The other one will have less but it should never have 0 volts. That's the terminal that will provide important information.

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