How To Test The Alternator (1996-2001 4.0L Ford Ranger And Mazda B4000)

By: Abraham Torres-Arredondo
Created: 13 September 2012
Updated: 17 March 2024
Articl Id: 101

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TEST 2: Testing The Continuity Of The Alternator's Battery Circuit

How To Test The Alternator (1996, 1997, 1998, 1999, 2000, 2001 4.0L V6 Ford Ranger And Mazda B4000)

The battery receives the alternator's voltage and amperage output across a single wire.

One end of this wire connects to the positive (+) battery post, and the other connects to the rear of the alternator. The arrow in the photo above points to the wire's connection on the back of the alternator.

A mega fuse or inline fusible links protect this output wire. In this test section, you'll check the condition of the mega fuse or fusible links with a simple multimeter continuity test.

You can consult the following wiring diagram to determine if your particular Ford Ranger (Mazda B4000) has inline fusible links or a mega fuse protecting this circuit.

Let's get testing:

1
Disconnect the battery negative (-) terminal from the battery. Do not proceed to the next steps till you do this first.

NOTE: Leave the battery positive (+) cable connected to the battery.
2
Set your multimeter to Ohms mode.
3
Connect the red multimeter test lead to the stud behind the alternator. This stud is where the big wire, that supplies the alternator's output to the battery, is attached to with a nut.

The arrow in the photo above points to the stud location.
4
Connect the black multimeter test lead to the battery positive (+) terminal.
5
Your multimeter should register about 0.5 Ohms to 1 Ohms if the inline fusible link or mega fuse is not blown.

If the inline fusible link or mega fuse is blown, your multimeter will register an infinite Ohms reading (OL).

Alright, let's interpret your test results:

CASE 1: Your multimeter registered continuity (0.5 to 1 Ohms). This result indicates that the inline fusible links or mega fuse is OK and not blown.

So far, it's looking like the alternator is bad. You still need to perform one last test. For this test, go to: TEST 3: Checking The Alternator Fuse.

CASE 2: Your multimeter DID NOT register 0.5 to 1 Ohms, it registered OL. This result tells you that the inline fusible links or mega fuse is blown.

You'll need to replace the inline fusible link or mega fuse and re-test the battery's voltage with engine running. This should solve your no-charge condition.

TEST 3: Checking The Alternator Fuse

In your Ford 4.0L Ranger or Mazda B4000, the alternator's voltage regulator receives 12 Volts.

Once the engine starts and runs, these 12 Volts activate the alternator to charge the battery.

These 12 Volts are delivered by the yellow with white stripe (YEL/WHT) wire of the alternator's voltage regulator's connector. The orange arrow in the photo above points to the location of this connector.

A dedicated alternator fuse or an inline fusible link protects the YEL/WHT wire.

In this test section, you'll check the condition of the fuse or inline fusible link.

These are the test steps:

1
Reconnect the battery to its battery negative (-) cable.
2
Disconnect the voltage regulator from its electrical connector.
3
Place your multimeter in Volts DC mode.
4
Connect the black multimeter test lead directly to the battery negative (-) terminal.
5
Probe the yellow with white stripe (YEL/WHT) wire on the alternator's voltage regulator connector with the red multimeter test lead.
6
Your multimeter should register one of two things:

1.) 10 to 12 Volts DC, if the fuse (fusible link) is good.

2.) 0 Volts DC, if the fuse (fusible link) is blown.

Let's take a look at what your specific test results mean:

CASE 1: The multimeter registered 10 to 12 Volts. This is the correct and expected test result. This result lets you know that the fuse (fusible link) is OK.

You can conclude that the alternator is bad and needs replacement if you have:

Confirmed that the battery voltage is NOT at 13.5 to 14.5 Volts DC with the engine running (TEST 1).
Confirmed that the alternator's output wire has continuity (TEST 2).
Confirmed, in this test section, that the YEL/WHT wire has 10 to 12 Volts.

CASE 2: The multimeter DID NOT register 10 to 12 Volts. Please replace the fuse or fusible link with another of the same amperage rating and repeat TEST 1.