How To Test The Alternator (2001-2007 3.3L Chrysler And Dodge Mini-Van)

TEST 2: Checking The Continuity Of The Bat (+) Cable

Your mini-van's alternator supplies the battery the current it needs across a single heavy gauge wire. This wire connects to the alternator's stud with a nut (this stud is known as the B + terminal).

This B + wire doesn't connect directly to the battery's positive (+) terminal. It first connects to the starter motor solenoid across an inline 10 gauge fusible link. From there it connects to the battery's positive (+) terminal.

Now, this inline 10 gauge fusible link can get blown. Once it's blown, the alternator's output can not reach the battery.

So in this test step, you're going to verify that this inline-fusible link is OK with a simple multimeter continuity test.

NOTE: The battery negative terminal must be disconnected from the battery negative post to perform this continuity test.

This is what you'll need to do:

1. 1

   Disconnect the battery negative (-) cable terminal from the battery negative post. The positive cable remains connected.
   
   IMPORTANT: Don't continue to the next step without first disconnecting the negative cable from the negative battery post.

2. 2

   After disconnecting the battery negative (-) cable, turn on your multimeter and select Ohms mode.
   
   IMPORTANT: The engine must be cold to perform this test, or you run the risk of getting burned by the engine's hot surfaces!

3. 3

   Your Chrysler mini-van'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.

4. 4

   With the black multimeter test lead, probe the center of the battery positive post on your Chrysler mini-van's battery.

5. 5

   You'll get one of two results.
   
   1.) If the inline fusible link, protecting this circuit, is blown your multimeter will indicate a reading of OL (which means over limit). In other words, there will be NO continuity.
   
   2.) If the inline fusible link is OK and not blown, your multimeter will register an Ohms reading of 0.5 Ohms or less. In other words, there will be continuity.

Let's take a look at what your results mean:

CASE 1: Your multimeter registered continuity. This is good, since it indicates that the inline fusible link protecting this circuit is OK and not blown.

If the alternator is still not charging the battery (let's say you've already replaced the alternator and it didn't solve the problem), take a look at: TEST 3: Part 1 -Alternator Is New But It Still Doesn't Charge The Battery.

CASE 2: Your multimeter DID NOT register continuity. This result tells you that the 12 gauge inline fusible link is blown and this will keep the alternator from charging the battery.

As I mentioned earlier, in this test section, this 12 gauge inline fusible link is part of the Bat + wire. It's on the end of the Bat + wire that connects to the starter motor solenoid.

Your next step is to check and replace this inline fusible link (if applicable) and retest. Replacing this 12 gauge inline fusible link (if blown) should solve your no-charge condition. You'll have to investigate the reason this inline fusible link blew, since they don't get blown for no particular reason.

TEST 3: Part 1 -Alternator Is New But It Still Doesn't Charge The Battery

There's a good chance that you have replaced the alternator but the battery light is still on and the alternator isn't charging the battery.

If this is happening in your particular case, this section may offer some insights on what direction you need to take your alternator diagnostic/troubleshooting.

The most fundamental piece of information we need to know about your 3.3L Chrysler mini-van's alternator is that this bad boy is computer controlled.

The alternator's voltage regulator is located inside your mini-van's PCM (Powertrain Control Module = fuel injection computer) and is known in Chrysler tech-speak as the Electronic Voltage Regulator (EVR) circuit.

The PCM also uses a Battery Temperature Sensor (BTS) to control the alternator and this bad boy (the BTS) is also part of the internal circuitry of the PCM. In other words, this sensor is also part of the PCM. Its job is to sense battery temperature so that the PCM can adjust the alternator's charging rate.

Since the alternator is computer controlled, the PCM sets specific alternator diagnostic trouble codes when a fault occurs:

• P0622: Generator Field Not Switching Properly.
• P1492: Battery Temperature Sensor Voltage Too High.
• P1493: Battery Temperature Sensor Voltage Too Low.
• P1594: Charging System Voltage Too High.
• P1682: Charging System Voltage Too Low.

The one component of the two (inside the PCM) that we can test is the electronic voltage regulator (EVR) and in the next section I'll explain how.

TEST 3: Part 2 -Testing The Voltage Regulator Inside The PCM

Before I go into the test details, let me give you some background info on the electronic voltage regulator, EVR for short and located inside your mini-van's PCM, that'll help you make sense of the test itself.

One: It's connected in series with the alternator and Ground (making it possible to tap into the circuit and test the EVR).

Two: The electronic voltage regulator (EVR) controls the alternator's voltage/amperage output by cycling the Ground on and off very fast (this is called pulse-width modulation). By the way, another component that works on this very same principle is a fuel injector where the computer controls its ‘open’ time by opening and closing its Ground path (pulse with modulation).

In the case of your mini-van's alternator, this ‘open’ time (caused by the cycling of the Ground path by the EVR) is what increases or decreases its voltage and amperage output.

Thankfully, you and I can verify if this is occurring (the pulse-width modulation of the Ground circuit by the EVR) by connecting your multimeter to the GEN FLD wire, of the alternator's harness connector and doing a simple multimeter voltage test with the engine running.

Now, while testing this pulse-width modulation with a multimeter, you're not gonna' see the voltage reading turn on and off because the cycling of the circuit is done very fast and the multimeter is not capable of showing it (only an oscilloscope can) but you will see an average of this cycling on and off, which the multimeter will translate into a number.

NOTE: You need to perform this test on a cold engine, or you run the risk of getting burned by a hot engine while connecting your multimeter to the GEN FLD wire of the alternator's harness connector (if the engine has been running for any length of time).

This is what you need to do:

1. 1

   Disconnect the battery negative (-) cable terminal from the battery negative post. The positive cable remains connected.

2. 2

   Connect the multimeter's black test lead to the generator field (GEN FLD) wire of the alternator's 2 wire connector.
   
   This is the BRN/GRY wire of the alternator's harness connector.
   
   Since the alternator must remain connected to its harness connector, you'll need to use a wire piercing probe to connect your multimeter's black lead to this wire (see: Wire Piercing Probe).

3. 3

   Set your multimeter to Volts DC mode.

4. 4

   Connect the red multimeter test lead to the battery's positive (+) post.

5. 5

   At this point, reconnect the battery negative (-) cable to the battery negative (-) post.
   
   Before you continue to the next step, make sure that your multimeter test leads/wires are not gonna' get tangled with the engine's serpentine belt.

6. 6

   Start the engine and notice the voltage output of the multimeter.
   
   Once the engine idle stabilizes, note the voltage number your multimeter is displaying. You many notice that this number fluctuates a little and this is normal.
   
   NOTE: There's no specific number to give you or that you should expect because the EVR's pulse-width modulation of your specific mini-van is unique to the actual operating conditions and charge level of your mini-van's battery.

7. 7

   Have a helper turn on all accessories possible like the headlights, rear window defroster, A/C, radio, etc.
   
   Your multimeter should now show an increase in the voltage number. This value should be higher than the value you saw when the engine was idling and with everything off.

8. 8

   Have your helper turn off all the things he (or she) turned on in step 5.
   
   Your multimeter should now show a decrease in the voltage number. This value should be lower than the value you saw when the engine was idling and with everything on.
   
   NOTE: Keep in mind that if the EVR is good and doing its job, the voltage value your multimeter registers will fluctuate as it increases and decreases and this is normal. In other words, don't expect the voltage number to increase and decrease in a steady linear manner. The important thing to see here is that the voltage values increase and decrease as you apply or remove the electrical loads created by the headlights, rear window defroster, etc.

Let's take a look at what your test results mean:

CASE 1: Your multimeter registered an increasing/decreasing voltage as you applied and removed the electrical loads. This result tells you that the electronic voltage regulator (EVR) inside the PCM is working and trying to control the alternator's amperage/voltage output.

CASE 2: Your multimeter DID NOT an increasing/decreasing voltage as you applied and removed the electrical loads. This result usually tells you that the EVR is bad and that the PCM needs to be replaced.

Before you run out and replace the PCM, you need to:

1. Check that there isn't an ‘open-circuit’ problem in the GEN FLD circuit between the PCM and the alternator's harness connector.
2. That the alternator's 2-wire harness connector isn't damaged or broken.
3. That the alternator is good by having it bench-tested at your local auto parts store.
   • New or rebuilt alternators can be defective right out of the box and this happens a lot!
4. Check all of the PCM's Ground circuits by doing a voltage drop test on them and repairing any corrosion issues that the voltage drop test finds.
5. That the battery's terminals and posts are corrosion free.

Now, if the above is beyond your diagnostic skills, don't hesitate to get a professional tech's opinion and/or advice.