How-to: Alternator voltage test. - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars
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post #1 of 1 (permalink) Old 02-26-12, 04:48 PM Thread Starter
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Read How-to: Alternator voltage test.

Reply to: 2001 Mustang Alternator Issues...

You need to check the wiring. Start simply. When it doesn't charge next time wiggle or move the 3 way connector and its wiring. If it starts charging intermittently as you do this, there is an issue with the connector terminals being spread open, or the wires be partially broken right near the connector or where the wires enter the connector. new connector from Ford is the fix.

If wiggling doesn't change anything get a voltmeter. With the negative lead clipped to the negative terminal, disconnect the three way connector and probe the terminal of the Yellow/White wire with the positive lead. There should be battery voltage here at all times. Next, probe the terminal of the Light Green/Red wire. There should be battery voltage or close to it. Probe the heavy battery lead (Black/Orange) at the alternator. Should be battery voltage. Last test is voltage drop from positive cable clamp to the heavy battery lead on the alternator. Clip the positive lead of the meter to the positive cable clamp. probe the heavy lead on the alternator with the negative test lead. There should be 0.5V or less. This should be a start for you, diagram is below.

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