Testing your alternator to see if it's the cause of the battery light being illuminated on your instrument cluster is an easy test that you can accomplish in under 15 minutes on your Ford Escort (or Focus, Tracer, or any 1.9L or 2.0L Ford vehicle).
In this article, I'll show you how to do an alternator test using just a multimeter and in three easy steps. This simple test will let you know if the cause of the No Charge Condition is due to a BAD alternator or not.
Contents of this tutorial:
ALTERNATOR TEST 1: Checking Output Voltage with a multimeter
To be able to accomplish this test and get a conclusive result from it you'll need to have the car running for about 10 to 15 minutes and so it's important that the battery in your Ford car be with a full charge (to keep the car running). So if you know the battery doesn't have a charge, please take the time to charge it first.
Since you'll be working around the engine while it's running, please take all necessary safety precautions.
OK, this is what you'll need to do:
Grab your multimeter and set it on Volts DC mode.
Crank and start the car.
Now, check the battery's voltage by probing the positive battery terminal with the RED multimeter test lead and probing the negative battery terminal with the BLACK test lead.
Your multimeter will display one of the following two voltage results:
1.) A steady 13.5 to 14.5 Volts DC.
2.) Or 12.5 Volts that will decrease the longer the engine stays running.
The next steps are to place an electrical load on the alternator to further confirm that it's either working OK and charging or not.
You can easily do this by turning On every accessory possible that needs electricity to run. 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.
As all this stuff is being turned On, observe your multimeter's voltage readings. The multimeter will display one of the two following results...
1.) The multimeter will continue to register a steady 13.5 to 14.5 Volts DC no matter what gets turned on or...
2.) a 12.5 V DC voltage that will decrease down to 10 Volts DC the more things get turned on inside the car.
Take a look at the following test interpretations to find out which one best fits your multimeter test results:
CASE 1: If your multimeter registered 13.5 to 14.5 Volts. This is good and it tells you that the alternator is working and is charging the battery and providing enough juice for the electrical needs of your Ford Escort (or Focus, Tracer, or 1.9L or 2.0L Ford vehicle).
No further testing is required, since this multimeter test result eliminates the alternator on your Ford as BAD.
CASE 2: If your multimeter registered a voltage that steadily dropped down to 9 Volts: This is a clear indication that your Ford's alternator IS NOT charging the battery.
Replacing the alternator at this point usually solves around 90% of the No Charge Conditions on any Ford Escort (or Focus, Tracer, or 1.9L or 2.0L Ford vehicle) 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, TEST 2: Checking For a Blown Mega Fuse.