How To Test The Alternator (1993-1997 2.3L Ford Ranger)

Testing the alternator, while still on your 1993-1997 2.3L Ford Ranger, is easier than you think!

Not only that, but it can be accurately tested with just a simple multimeter and in this tutorial I'll show you how to.

You can find this tutorial in Spanish here: Cómo Probar El Alternador (1993-1997 2.3L Ford Ranger) (at: autotecnico-online.com).

Symptoms Of A Bad Alternator

The alternator is one of the many critical components your 2.3L Ford Ranger needs to be able to start and stay running.

Why? Well, because the alternator has two main jobs. This first is to charge your vehicle's battery so that you crank and start the engine each and every time you need to.

The other is to provide the electrical current for everything that requires it (for example: the ignition coil, the fuel pump, the radio, the blower motor, the headlights, etc.), as you're driving down the road or just idling in traffic.

So, when the alternator fails, you'll notice one or several of the following symptoms:

1. The battery light, on the instrument cluster, stays on after the engine starts (when it should be off).
2. The headlights glow very dim when you turn them on (night driving).
3. Your Ranger won't crank. It will only crank and start if you jump start it.
4. The only way your Ranger cranks and starts is if you charge the battery.
5. The idle may get high when you come to a stop.

TEST 1: Battery Voltage Test With Engine Running

To get your alternator diagnostic on the way, the first you need to do is check what the battery's voltage is with your 2.3L Ford Ranger's engine running.

You'll need a multimeter for this test and this bad boy can be an old style analog meter or a digital one.

Now, to get into specifics: The purpose of this test is to see if your multimeter will register a battery voltage of 12.5 Volts DC or higher (while the engine is running that is) or if the voltage is 12.5 Volts or less.

If your 2.3L Ford Ranger's alternator is OK and charging (not defective), your multimeter will show a voltage of 13.5 to 14.5 Volts DC.

If the alternator is bad and NOT charging the battery, your multimeter will show a voltage of 12.5 Volts DC or less.

NOTE: If the battery is completely dead on your 2.3L Ford Ranger, you'll need to charge it up enough so that the car can idle for about 5 to 10 minutes (while you perform the test).

These are the test steps:

1. 1

   Crank and start your 2.3L Ford Ranger and select Volts DC mode on your multimeter.

2. 2

   Probe the positive battery terminal with the red multimeter test lead.
   
   With the black multimeter test lead, probe the negative battery terminal on your 2.3L Ford Ranger's battery.

3. 3

   Your multimeter is gonna' register one of two possible readings and they are:
   
   1.) A steady 13.5 to 14.5 Volts DC.
   
   2.) Or 12.5 Volts that will decrease the longer the engine stays running.

1. 4

   Put an electrical load on the alternator to further confirm that it's either charging or not charging.
   
   You can do this by turning on every accessory possible (inside the vehicle). For example: Turn on the A/C or heater on high, turn on the windshield wipers, turn on the headlights, turn on everything and anything that uses electricity inside and outside of the vehicle.

2. 5

   Your multimeter will show you one of two things (as you turn on all of this stuff):
   
   1.) The multimeter will register a nice and steady 13.5 to 14.5 Volts DC no matter what gets turned on.
   
   2.) It will register 12.5 V DC and this voltage will decrease more and more as you turn on stuff inside your Honda vehicle.

OK, let's interpret your multimeter test results:

CASE 1: Your multimeter registered 13.5 to 14.5 Volts. This voltage test result tells you that the alternator is working (charging the battery).

No further testing is required, since this multimeter test result eliminates the alternator on your 2.3L Ford Ranger as bad.

Now, if you're having to jump-start the car to get it going, this test result points to a bad battery or a parasitic drain. A parasitic drain is tech-speak for something staying on (usually inside the car, for example: a dome-light) and draining the battery while the engine is off.

CASE 2: Your multimeter registered a voltage that steadily dropped down to 9 Volts. This is a clear indication that your 2.3L Ford Ranger's alternator IS NOT charging the battery.

Replacing the alternator at this point usually solves around 90% of the No Charge conditions on any 2.3L Ford Ranger around the world. That's right, you could stop testing here and say: ‘The alternator is fried’ and be done but..

I suggest two more easy tests to be absolutely sure it is bad. For the first test of the two, go to: TEST 2: Checking The Continuity Of The Bat (+) Cable.