How to Test a BAD Alternator
(Ford 3.0L, 3.8L)

How to Test a BAD  Alternator (Ford 3.0L, 3.8L)

This article will help you to test and troubleshoot a No Charge Condition on any Ford (and Mercury and Lincoln) 3.0L and 3.8L V6 equipped car, pick up or mini-van.

The only piece of diagnostic/testing equipment you’ll need to test the Alternator and to follow the step-by-step instructions, is a Multimeter (doesn’t matter if it’s a Digital or Analog Multimeter).

If you need to see if this Alternator Test Article applies to your specific Ford vehicle... on the column on the right, you’ll see a container with the heading ‘Applies To:’ that will have a list of Ford, Mercury, and Lincoln vehicles this article applies to.

Here are the contents of this article at a quick glance:

  1. ALTERNATOR TEST 1.
  2. ALTERNATOR TEST 2.
  3. ALTERNATOR TEST 3.
  4. Symptoms of a BAD Alternator.
  5. Related Test Articles.

ALTERNATOR TEST 1

This is an On-Car test of your Ford’s Alternator. This first test is done with the engine running, so you have to be careful, alert, and take all necessary safety precautions.

The most important part of this first Alternator test is that you need to make sure that the Battery is fully charged before starting this test, since you’ll need to have the engine running for the duration of this first test.

Well, without further ado, this is what you need to do:

  1. 1

    Start the engine and place your Multimeter in Volts DC mode. Again, be careful, since you’ll be working around a running engine.

  2. 2

    Place the RED Multimeter Test Lead on the Battery Positive Terminal and the BLACK Multimeter Test Lead on the Battery Negative Terminal.

  3. 3

    Your Multimeter will register one of two things (depending if it’s charging the Battery or not). It will either:

    1.) Show a steady DC Volts reading of about 13.5 to 14.5 Volts the whole time the engine is running or

    2.) Show a Voltage of about 12.5 Volts that decreases the longer the engine is running.

  4. 4

    The next step is to have an assistant turn on everything and anything that uses electricity inside the vehicle like: headlights, windshield wipers, turn signals, a/c or heater blower on high, etc.

    This will put an electrical load on the Alternator to either confirm it’s really working or it’s fried.

  5. 5

    Observe the Multimeter’s readings, since your Multimeter will react to the things that are turned on (if it’s BAD). OK, here’s what is going to happen...

    The Multimeter’s reading will continue to drop down to about 9 Volts or more (the vehicle may stall around 9 Volts) or the Voltage reading will stay steady around 13.5 to 14.5 Volts the whole time.

    OK, let’s interpret your Multimeter Test results in the next page...

Continued in the next page...

Ford Vehicles:

  • Aerostar 3.0L
    • 1992, 1993, 1994, 1995, 1996, 1997
  • Mustang 3.8L
    • 1997, 1998, 1999, 2000, 2001, 2004
  • Probe 3.0L
    • 1990, 1991, 1992
  • Ranger 3.0L
    • 1991, 1992, 1993, 1994, 1995, 1996, 1997

Ford Vehicles:

  • Taurus 3.0L, 3.8L
    • 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
  • Tempo 3.0L
    • 1992, 1993, 1994
  • Thunderbird 3.8L
    • 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997

Lincoln Vehicles:

  • Windstar 3.0L, 3.8L
    • 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003

Lincoln Vehicles:

  • Continental 3.8L
    • 1989, 1990, 1991, 1992, 1993, 1994

Mercury Vehicles:

  • Cougar 3.8L
    • 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997
  • Sable 3.0L, 3.8L
    • 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
  • Topaz 3.0L
    • 1992, 1993, 1994

Mazda Vehicles:

  • B3000 3.0L
    • 1994, 1995, 1996, 1997

“I bought a perfect second car... a tow truck.”
Rodney Dangerfield

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