An alternator diode is being tested using a digital multimeter set to the diode check position. a good diode will read if the leads are connected one way across the diode and if the leads are reversed.

Usually a faulty instrument voltage regulator will produce a few symptoms that can alert the driver of a potential issue.

Dim or flickering gauges. One of the first symptoms of an issue with the voltage regulator is dim or flickering gauges. ...

Inaccurate or erratic readings. ...

Inoperable instrument cluster.

Explanation:

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