Testing to see if the alternator is bad or not, on your Ford 4.6L or 5.4L equipped E-Series van, is a simple test that can be done with just a multimeter.
This is a test that you can do with the alternator still in the vehicle and in this article, I'll show you just how to do it.
Contents of this tutorial:
APPLIES TO: This tutorial applies to the following vehicles:
- 4.6L, 5.4L V8 Ford E150: 1997, 1998, 1999, 2000, 2001, 2002, 2003.
- 4.6L V8 Ford E250: 1997, 1998, 2003.
- 5.4L V8 Ford E250: 1997, 1998, 1999, 2000, 2001, 2002, 2003.
- 5.4L V8 Ford E350: 1997, 1998, 1999, 2000, 2001, 2002, 2003.
Crown Vic And Grand Marquis: You can find the alternator test for the Crown Vic and Grand Marquis here:
F-Series Pickups: You can find the alternator test for the F-Series pickups here:
- How To Test The Alternator (1997-2003 4.6L, 5.4L Ford F150, F250, F350) (at: easyautodiagnostics.com).
NOTE: This tutorial applies to several other Ford, Mercury, and Lincoln vehicles equipped with a 4.6L or 5.4L V8 engine. You can see the application list in the 'Applies To' box on the left if you're using a desktop or at the bottom of this page if you're using a hand-held mobile device.
WIRING DIAGRAM: The alternator circuit wiring diagram for the 1997-2003 4.6L/5.4L Ford E150, E250, and E350 can be found here:
- Alternator Circuit Wiring Diagram (1997 4.6L, 5.4L V8 Ford E150, E250, E350).
- Alternator Circuit Wiring Diagram (1998-2003 4.6L, 5.4L V8 Ford E150, E250, E350).
Symptoms Of A Bad Alternator
When you turn the key, the starter motor kicks in. And let me tell you, this bad boy uses a lot of power from the battery to crank the engine and get it running.
Once the engine fires up and starts running, the starter motor's job is done, and it stops drawing power from the battery. Now the alternator takes over and starts recharging the battery.
This ensures that the battery has enough power stored for the next time you need to start the engine. Besides charging the battery, the alternator also powers your van's electrical systems (like the headlights, radio, and air conditioning) when the engine is running.
Unfortunately, the alternator isn't gonna last forever. When it fails, you're gonna see one or more of the following symptoms:
- The battery light will is illuminated in the vehicle's instrument cluster.
- The headlights are dim when the vehicle is running and they are turned On. They grow dimmer as time passes till eventually the vehicle stalls.
- The vehicle requires a jump-start, every time it's turned off, to start it.
- The battery needs to be constantly re-charged.
TEST 1: Battery Voltage Test With Engine Running
The battery on your Ford (or Lincoln or Mercury) vehicle must be fully charged for this test since you'll need to have the vehicle with the engine running.
Also, you can use a digital or analog multimeter. Both types of multimeters will do the job! One last thing, you'll be working around a running engine, so be careful and take all necessary safety precautions.
OK, here's the first test:
- 1
Start the engine and let it idle.
- 2
Place your multimeter in Volts DC mode.
- 3
Check the battery's voltage with your multimeter.
- 4
The multimeter should register 13.5 to 14.5 Volts.
If it doesn't, don't worry about this just yet, continue to the next step. - 5
Turn on every accessory possible while observing the multimeter. Like the headlights, the A/C or heater (high blower speed), the windshield wipers, the radio, the rear window defroster, etc.
As each accessory comes on, they'll place a load on the charging system (alternator). - 6
The multimeter's voltage reading will decrease slightly and then stabilize around 13.5 to 14.5 Volts DC as each accessory comes on.
- 7
Let the engine run for about 5 minutes with all of the accessories on.
- 8
The battery voltage should remain between 13.5 to 14.5 Volts DC with all of the accessories on during the whole 5 minute duration.
OK, let's make sense of the readings that your multimeter recorded in the test:
CASE 1: Your multimeter registered 14 to 14.5 Volts from the start of the test to the end of the test. This test result lets you know that the alternator on your 4.6L or 5.4L Ford van is working like it should. No further testing is required.
CASE 2: Your multimeter DID NOT register 14 to 14.5 Volts from start to end and the voltage dropped to 9 Volts DC. This test result lets you know that the alternator is probably bad.
Probably bad? What I mean is this, around 90% of the time, you could stop here, replace the alternator and the problem is solved. To be 100% sure the alternator is bad, there are 2 more tests to do and I'll show you how to do them. Go to: TEST 2: Checking The Continuity Of The BAT + Circuit.
TEST 2: Checking The Continuity Of The BAT + Circuit
The voltage and amperage that the alternator delivers to the battery and the rest of the vehicle is delivered across one single cable.
This cable is the black with orange stripe (BLK/ORG) cable that connects to the stud on the rear of the alternator (the arrow in the photo above points to this stud).
Before this juice reaches the battery via the BLK/ORG cable , it has to cross two inline fusible links.
Before we can condemn the alternator as bad, we need to make sure that the fusible links between the alternator and the battery are not blown. Cause if they're blown, the alternator could be working OK, but unable to deliver its output to the battery.
Verifying if the fusible links are blown or not can be done with a simple multimeter resistance test (Ohms).
These are the test steps:
- 1
Disconnect the battery negative (-) cable from the battery but leave the positive (+) cable connected to the positive (+) post.
IMPORTANT: Do not proceed to the next steps until you have done this first. - 2
Set your multimeter to Ohms mode.
- 3
Connect the red multimeter test lead to the stud shown in the photo above.
The BLK/ORG connects to the stud indicated by the arrow (in the photo above).
NOTE: Don't disconnect the BLK/ORG cable from the alternator. - 4
Connect the black multimeter test lead on the battery positive (+) terminal (at the battery).
The battery negative (-) wire must remain disconnected from the battery. - 5
Your multimeter will register one of two values:
1.) Continuity (usually an Ohms value of about 0.5 Ohms).
2.) No continuity (an infinite Ohms reading (OL)).
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 result indicates that the mega fuse is OK and not blown.
Now, there's just one more thing to check and you're done! The next test is to make sure that the alternator's voltage regulator is getting power. For this test, go to: TEST 3: Making Sure The Voltage Regulator Is Getting Power.
CASE 2: Your multimeter DID NOT register 0.5 Ohms, it registered OL. This result tells you that the mega fuse is blown.
Inspect the inline fusible links. If they're blown, replace them and then repeat the continuity test followed by the battery voltage test with the engine running (TEST 1). This often resolves the issue of the alternator not charging.
I want to point out that blown fusible links are uncommon. So if they're blown on your van, it's important that you figure out what caused them to get blown (since it indicates an underlying problem).
LOCATION: These fusible links are connected to the starter motor relay (not the starter motor solenoid). You'll find the starter motor relay in the right front corner of your van's engine compartment.
