My scan tool and my DVOM disagree.

[GhostTypeP0300]

My scanner says that my battery and alternator are bad but my meter readings look good.

 

[GhostTypeP0300]

My scanner says that my battery and alternator are bad but my meter readings look good.

CES

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Available voltage @ the battery with the engine off. Negative to negative positive to positive.

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At the battery with the engine running and loads off.

 

[GhostTypeP0300]

Available voltage at the alternator -red lead to the alternator output post and black lead to battery negative with engine running and loads off.

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[BLACK'98DSM]

Low voltage at the OBD port or a junk scanner.

 

[GhostTypeP0300]

Loads on.

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[GhostTypeP0300]

Voltage drop test of the alternator output cable.red to alternator stud, black to battery +.
The voltage drop was .55 so cable was upgraded to a 4 gauge cable. From two 8 gauge cables that are wired in parallel from the factory.

 

[GhostTypeP0300]

Voltage drop of the ground side next. Measure negative circuit voltage drop by placing the black lead of the voltmeter on the housing of the alternator and the red lead of the voltmeter on the negative battery terminal. If the reading is less than 0.03 volts, verify the alternator is charging and retest.