STARTER TEST 2: Verifying The Start Signal
In the first starter motor test (in the previous page) you applied 12 Volts to the starter motor, in this test step, you're gonna' check to see if the starter motor solenoid is receiving the Start signal.
As you may already know, this Start signal usually originates from the ignition switch.
One last thing before we start, you can use either a multimeter or a 12 Volt automotive test light. I personally prefer a multimeter but a 12 Volt test light will work.
OK, here's what you'll need to do:
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Raise your Ford car and place it on jack stands. Remember, think safety all of the time!
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From underneath the vehicle, probe the wire that attaches to the S Terminal on you car's starter motor solenoid with the red multimeter test lead. You can accomplish this by using a tool like a Wire-Piercing Probe or any other suitable tool you can use to pierce the wire and attach the red multimeter test lead to.
You might be asking yourself which wire is the one that connects to the S Terminal on the starter solenoid, well this is the thinnest of the two wires that connects to the starter solenoid. The big thick wire is the one that comes from the battery and the thinnest one (S Terminal Wire) is the one that delivers the Start signal from the ignition switch (or starter relay). - 3
Now, the black multimeter test lead has to be grounded to a clean and rust-free spot on the engine or directly on the battery negative (-) terminal.
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Although the car won't crank, when ready, have a helper crank the engine while you eye-ball the multimeter's display screen.
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Your multimeter is going to register one of two results:
1.) It'll register 10 to 12 Volts if the ignition switch (or starter relay) are working.
2.) It'll register 0 Volts if something in those circuits is wrong.
OK, let's make sense of the readings that your multimeter recorded in the test:
CASE 1: Your multimeter registered 10 to 12 Volts. This let's you know that both the ignition switch and the neutral safety switch are doing their job and supplying the Crank (Start) Signal.
Now, around 90% of the time, you could stop here and condemn the starter motor as bad and replace it and the problem would be solved. But to be absolutely sure, I suggest doing one more test.
The next test would be to voltage drop test the battery positive wire that connects to the starter motor with the nut. This is an easy and fast test, go to: STARTER TEST 3.
CASE 2: If your multimeter DID NOT register 10 to 12 Volts. This tells you that the either the ignition switch or the neutral safety switch or the starter relay is bad. Without this Start (Crank) signal, the starter motor will not come alive and crank the engine.
Now, it's beyond the scope of this article to test either the ignition switch, the neutral safety switch, and starter relay but you have at least eliminated the starter motor itself as bad.
