How To Test The Alternator (2001-2002 4.7L Dodge Dakota)

The Basics Of The Electronic Voltage Regulator (EVR)

The alternator's voltage regulator is located inside the PCM of your Dodge Dakota (Durango) and is known as the EVR (Electronic Voltage Regulator).

Since the EVR is connected in series with the alternator and Ground, we can tap into the alternator's GEN FLD wire (with a multimeter) and test the EVR output.

In a nutshell, this is how it works: The Electronic Voltage Regulator (EVR) controls the alternators 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 my opening and closing its Ground path (pulse with modulation).

In the case of your Dakota's (Durango'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.

You can find the EVR multimeter test here: TEST 3: Testing The Electronic Voltage Regulator Output.

More 4.7L Dodge Tutorials

You can find a complete list of 4.7L Dodge tutorials in this index:

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