Testing to see if the alternator in your Honda Accord, or Odyssey or Prelude is bad or not is a very easy test to do. All you need is a multimeter and in this article I will show you how to do this fast and simple test.
This article is a part of a series of Honda testing and troubleshooting articles, that I've written, and at the end of this article you'll find all of the links to the others.
Contents of this tutorial:
ALTERNATOR TEST 1: Testing Battery Voltage With The Engine Running
The very first thing you need to do is verify what the voltage of the battery is with the engine running. This will let you know if the alternator is charging and providing enough juice for the electrical needs of your Honda car or not.
OK, for this test to be effective (well, for it to work), you need to make sure that the battery has enough of a charge to keep the engine running for about 20 minutes (more or less). So if the battery in your Honda is completely dead, charge it up first.
And since this very first test is done with the engine is running, you need to be careful, be alert and take all necessary safety precautions.
Alright, I'm done talking. Let's get testing, this is what you need to do:
Crank and start your Honda and turn on your multimeter and select Volts DC mode on it.
Probe the positive (+) battery terminal with the red multimeter test lead. With the black multimeter test lead, probe the negative (-) battery terminal on your Honda'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.
Now, the next step will put an electrical load on the alternator and will further confirm that it's either charging or not.
You need to turn every accessory possible inside the vehicle. 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 you're turning on all this stuff, keep your eyes on your multimeter's voltage reading. Here's what is going to happen, you'll one of the two following results:
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:
Take a look at the following test interpretations to find out which one best fits your multimeter test results:
CASE 1: 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 Honda Accord, or Odyssey or Prelude.
No further testing is required, since this multimeter test result eliminates the alternator on your Honda as bad.
CASE 2: Your multimeter registered a voltage that steadily dropped down to 9 Volts. This is a clear indication that your Honda's alternator IS NOT charging the battery.
Replacing the alternator at this point usually solves around 90% of the no-charge conditions on any Honda Accord (or Odyssey or Prelude or any 2.2L, 2.3L Honda) 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 ALTERNATOR TEST 2: Checking The Continuity Of The Bat (+) Cable.