ALTERNATOR TEST 2: Checking The Continuity Of The Bat (+) Cable
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 Accord (or Odyssey or Prelude). 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: TEST 3.
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.
ALTERNATOR TEST 3: Checking The Alternator Fuse
Your Honda Accord (or Odyssey or Prelude) will have a Fuse Box under the dash, and in this Fuse Box is another fuse that the alternator needs to start charging the vehicle.
This fuse is usually a 7.5 amp plastic blade type fuse. You may need to consult with your Owner's Manual once again if the fuses are not labeled.
Reconnect the battery to its negative battery cable, that you disconnected in the previous test.
Locate the alternator fuse, which will be located in the fuse box in the engine compartment.
Once you have located the fuse, remove it and check that it's not blown.
If it is blown, replace it with a new one and repeat ALTERNATOR TEST 1.
Let's take a look at your test results:
CASE 1: The fuse is NOT blown. This is good and let's you know that the alternator has all of the power sources it needs to charge, since it isn't, this result also let's you know that the alternator is bad and needs to be replaced.
CASE 2: The fuse IS blown, then please replace the fuse with another of the same amperage rating and start the car and check to see if the alternator is now charging the battery by repeating ALTERNATOR TEST 1.