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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 Civic.
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 Civic 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.
ALTERNATOR TEST 2: Testing The Continuity Of The Bat (+) Circuit
All of the electrical power that the alternator produces, to charge the battery and to power any of your Honda's electrical needs, passes thru' a single 80 or 100 Amp fuse! If this fuse is blown, the alternator could be working, but its output will never reach the battery or any accessory in or on the car that needs a steady voltage and amperage value.
So in this test step, you're going to verify that this fuse is OK on your Honda Civic. This is what you'll need to do:
The very first thing you need to do is to disconnect the negative battery cable terminal from the battery negative post. This is very important. Don't continue to the next step without first doing this.
After disconnecting the negative battery cable, turn on your multimeter and select Ohms mode.
Your Honda's alternator has only one big wire attached to it. This wire is attached with a nut. So, place your multimeter's RED test lead on the stud to which this wire is connected to. The arrow in the photo points to this stud.
With the black multimeter test lead, probe the center of the battery positive post on your Honda's battery.
You'll get one of two results:
1.) If the 80 (or 100) Amp fuse, protecting this circuit, is blown, your multimeter will indicate a reading of OL (which means over limit).
2.) If the Inline Fusible Link (or fuse) is OK and not blown, your multimeter will register an Ohms reading of 0.5 Ohms or less.
OK, now that the testing part is done, let's take a look at what your results mean:
CASE 1: Your multimeter registered 0.5 Ohms. This is good, since it indicates that the fuse protecting this circuit is OK and not blown.
The last test to do also involves checking the condition of another fuse. Except that this is just a regular plastic blade type fuse found in the Instrument Panel's fuse box. OK, for this test, go to: ALTERNATOR TEST 3: Checking The Alternator Fuse.
CASE 2: Your multimeter DID NOT register 0.5 Ohms, it registered OL. This result tells you that the fuse is blown and this will keep the alternator from charging the battery.
Replace the fuse and retest. Replacing the fuse should solve your no charge condition. You'll have to investigate the reason this Inline Fusible Link or fuse blew, since they don't go bad for no particular reason.
You're probably wondering: So where's this 80 (or 100) amp fuse located at? Well, you'll need to consult your Owner's Manual (or a repair manual or a Google Search), but this fuse is always located in the Under Hood Fuse Box in the Engine Compartment.