How To Test The Alternator (1997-2003 4.2L V6 Ford E150, E250)

TEST 3: Making Sure The Voltage Regulator Is Getting Power

The alternator's voltage regulator, bolted to the back of the alternator, needs 12 volts to start producing a charge.

This voltage is delivered through the terminal labeled with the letter A of the regulator's 3-wire connector (see the illustration above).

On the 1997 E-Series vans, the wire connected to terminal A is yellow with a white stripe (YEL/WHT). On the 1998-2003 vans, it's an orange with light blue stripe (ORG/LT BLU) wire.

Regardless of the model year of your particular van, the 'A' wire is protected by an inline fusible link.

In this test, you'll verify that terminal A is delivering power (12 volts) to the alternator's voltage regulator. Terminal A should always have 12 volts present.

This is what you'll need to do:

1. 1

   Reconnect the negative (-) battery cable to the battery's negative (-) post,.

2. 2

   Disconnect the 3-wire pigtail connector from the alternator.
   
   This 3-wire connector connects to the alternator's voltage regulator.

3. 3

   Connect the black multimeter test lead to the battery negative (-) terminal.
   
   IMPORTANT: The multimeter test lead must connect to a clean spot on the battery's negative (-) terminal.

4. 4

   Connect the red multimeter test lead to the female terminal labeled with the letter A of the alternator's 3-wire pigtail connector (see the illustration above).
   
   NOTE: On the 1997 model year vans, terminal A should connect to a YEL/WHT wire. On the 1998-2003 model year vans, this wire should be an ORG/LT BLU wire.

5. 6

   Your multimeter should register 10 to 12 Volts DC.
   
   NOTE: Power is present at all times, no need to turn the key to the ON position.

Let's interpret your test result:

CASE 1: 10 to 12 Volts are present. This means that the alternator's voltage regulator is getting power.

Now, this test result, in conjunction with TEST 1 and 2, let's you now that the alternator on your Ford 4.6L or 5.4L equipped van is bad. Replace the alternator. Replacing the alternator will solve the no-charge condition on your vehicle.

CASE 2: The indicated voltage is not present. This tells you that the voltage regulator is not getting power.

Without these 12 Volts, the voltage regulator will not activate the alternator to start charging the battery.

Without this voltage (12 Volts), the alternator will NOT produce a charge. Check the inline fusible link, replace it if blown, and retest.

More 4.2L Ford E150 And E250 Test Tutorials

If this tutorial was helpful, be sure and take a look at all of the 4.2L V6 E150 and E250 diagnostic tutorials and wiring diagrams in this index:

• 4.2L Ford E150 And E250 Index of Articles.

Here's a sample of the tutorials you'll find there:

• How To Test The Throttle Position Sensor (1997-2000 4.2L V6 Ford E150, E250).
• How To Test Engine Compression (1997-2003 4.2L V6 Ford E150, E250).
• How To Test The Fuel Pump (1997-2000 4.2L V6 Ford E150, E250).
• How To Test The CKP Sensor With A Multimeter (1997-2003 4.2L V6 Ford E150, E250).