How To Test The Starter Motor (Dodge 3.9L, 5.2L, 5.9L)

STARTER TEST 1: Applying 12 Volts To The Starter Motor S Terminal

OK, this is what you signed up for! To get our starter motor diagnostic on the way, the very first thing we'll do is apply 12 Volts to the S terminal of the starter motor (see the photos in the image viewer).

You can disconnect the wire that attaches to the S terminal or you can leave it connected to it (to apply 12 Volts to the S terminal), whatever is easiest for you.

NOTE: Getting to the starter motor solenoid S terminal (to manually apply 12 Volts) can be a challenge. What I do is use a wire piercing probe to pierce the S terminal wire (while it's still connected to the S terminal) and then I connect my remote starter switch to it and proceed from there, I suggest you do the same (to see what this tool looks like, go here: Wire Piercing Probe Tool Review (Power Probe PWPPPPP01)).

OK, this is what you'll need to do:

1. 1

   Jack up your Dodge vehicle and place on it jack stands. Remember, to only way to gain access to the starter motor is from underneath the engine.

2. 2

   Disconnect the battery negative (-) terminal.
   
   You'll reconnect it back in one of the following steps, for now, it's a safety precaution as you set up the test.

1. 3

   Attach one of the remote starter switch's terminals to the S terminal of the starter motor solenoid.
   
   This is easier said than done, so take your time and make sure the connection is on the S terminal of the starter motor solenoid.
   
   Also, in case you're wondering, you can leave the starter motor solenoid's S terminal wire connected to the engine's wiring harness connector or not, the test will work either way.

2. 4

   Reconnect the battery negative (-) cable to the battery negative post.
   
   Connect the remaining remote starter switch ‘alligator’ type connector to the battery positive (+) terminal.
   
   Now, apply 12 Volts to the S terminal wire of the starter motor starter solenoid with your remote starter switch. As you apply these 12 Volts (to the S terminal wire of the starter motor solenoid), you'll get one of two results:

   1. The starter will activate and will turn over the engine
   2. -OR-
   3. The starter motor won't do a thing.

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

CASE 1: The starter motor came to life and cranked the engine. This test result lets you know that the starter motor is OK and functioning. It also tells you that the probable cause, of it not working when you turn the key to start the engine, is a lack of the 12 Volt Start signal on the S terminal of the starter motor solenoid.

The next step is to go to TEST 2 and see if the starter motor is getting the 12 Volt Start signal on the S terminal wire (circuit). Go to: TEST 2: Verifying The Start Signal.

CASE 2: The starter motor DID NOT crank the engine. This usually means that your starter motor is bad and needs to be rebuilt or replaced.

I suggest 2 more tests and these are make sure that the starter motor is getting its 12 Volt Start signal and to test the battery cable (that attaches to the starter motor solenoid) for corrosion. This can be accomplished very easily with a voltage drop test.

• Go to: TEST 2: Verifying The Start Signal.
• Go to: TEST 3: Voltage Drop Testing The Battery Cable.

STARTER TEST 2: Verifying The Start Signal

What makes the starter motor activate and crank the engine is the 12 Volt Start Signal it gets when you turn the key to start the vehicle.

So, in this test step, we're gonna' see if the starter motor solenoid is getting this 12 Volt Start signal on the S terminal wire.

You can use a multimeter or a 12 Volt automotive test light (although the following test steps assume you're using a multimeter). OK, here's what you'll need to do:

1. 1

   Lift the vehicle and place it on jack stands (if it isn't already up in the air). Now, while underneath it, connect the red multimeter test lead to the S terminal wire of the starter motor.
   
   You can either test for this signal with the S terminal wire connected to the starter motor or not, your choice.

2. 2

   Connect the black multimeter test lead to a clean and rust-free spot on the engine or on the vehicle frame.
   
   Here I'm going to recommend something to you: Use a battery jump start cable to Ground the black multimeter test lead to a clean Ground point on the engine. The reason why is that depending on how rusty and dirty the underneath of the vehicle, you may NOT be able to find a clean and rust-free spot to Ground the multimeter's black test lead.

3. 3

   Now, have your helper crank the engine.
   
   The engine won't turn over, but the idea is to verify that the starter motor solenoid is getting the 12 Volt start signal from the ignition switch.

4. 4

   Your multimeter is going to register one of two results: A voltage between 10 to 12 Volts DC or no voltage at all.

OK, let's make sense of the readings that your multimeter recorded in the test:

CASE 1: Your multimeter registered a voltage between 10 to 12 Volts. This test result lets you know the starter solenoid is receiving the Start signal (crank signal).

This means that we can forget about the safety neutral switch and the ignition switch being bad. OK, now the next test is to do a very easy and simple voltage drop test. Go to TEST 3.

CASE 2: If your multimeter DID NOT register 10 to 12 Volts. This result exonerates the starter motor. Your starter motor is not bad.

Here's the reason why: Without this 10 to 12 Volt Crank Signal, the starter motor will not crank the engine. Now, although it's beyond the scope of this article to test the neutral safety switch or the ignition switch, you have eliminated the starter motor and this means saving money by not buying a part your vehicle does not need.