One of the easiest tests to do on your 2.0L Mazda 626 is the alternator test. In this tutorial I am going to show you an easy and fast way to do it and the best part of all is that you need a multimeter only. This test is very accurate and will tell you if the alternator is bad or not.
Contents of this tutorial:
You can find this tutorial in Spanish here: Cómo Probar El Alternador (1998-2002 2.0L Mazda 626) (at: autotecnico-online.com).
Symptoms Of A Bad Alternator
You're probably already aware that the alternator on your 2.0L Mazda 626 has two jobs to do. The first one is to charge the battery so that you can crank and start the engine.
Once the engine starts, quite a few components need electrical current to function. For example: the wipers, the blower motor, the fuel pump, etc. So the alternator's second job is to provide the electrical current that all those components need (to function).
So, when the alternator fails in your 2.0L Mazda 626, you'll notice one or several of the following symptoms:
- The charge light (also known as the battery light) will be shining nice and bright on your 626's instrument cluster.
- Whenever you turn on the headlights (night driving), they glow very dim.
- The car won't crank. It will only crank and start if you jump start your Mazda 626.
- The only way the car cranks and starts is if you charge the battery.
- The idle may get high when you come to a stop.
TEST 1: Battery Voltage Test With Engine Running
The very first thing that we need to do is to find out what the battery voltage is. We'll check this voltage with the engine running on your Mazda 626.
This is a very simple test that we'll do with your multimeter in Volts DC mode. Now the purpose of this test is to find out if the alternator is charging the battery or not.
If the alternator IS NOT charging the battery, your multimeter will show a battery voltage of 12.5 Volts DC with the engine running. If the alternator is OK and charging the battery, your multimeter will read a voltage of 13.5 to 14.5 Volts DC.
Before you start this test, you need to make sure that the battery on your Mazda 626 is fully charged. If the battery isn't charged then you need to make the time to charge the battery before you start any of these tests.
These are the test steps:
Crank and start your Mazda 626 and select Volts DC mode on your multimeter.
Probe the positive battery terminal with the red multimeter test lead.
With the black multimeter test lead, probe the negative battery terminal on your Mazda 626's battery.
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.
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.
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 Mazda 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 Mazda 626 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 Mazda 626's alternator IS NOT charging the battery.
Replacing the alternator at this point usually would solve the No Charge condition on your 2.0L Mazda 626. 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 EGI INJ Fuse.