How to Intermittently Test Starter Motor Components

An intermittent starter motor problem is one of the most frustrating issues you can deal with on a vehicle. The engine starts fine one moment, then refuses to crank the next. Because the failure isn't constant, most standard tests miss it entirely. That's exactly why a video guide to testing starter motor components intermittently is so useful it walks you through the process of catching a fault that only shows up some of the time, so you're not left guessing or replacing parts you don't need to replace.

What does "intermittent starter motor failure" actually mean?

An intermittent failure means the starter motor doesn't fail every time you turn the key. Sometimes the engine cranks and starts normally. Other times, you might hear a click, a grind, or nothing at all. This inconsistency is what makes it hard to diagnose. The starter motor, solenoid, relay, or wiring connection might work fine during a bench test but fail under real-world conditions heat, vibration, or a loose terminal can all cause problems that come and go.

For a deeper breakdown of individual parts and how to test each one, you can check this starter motor component testing walkthrough.

Why can't I just test the starter once and call it good?

You can, and sometimes that's enough. But with intermittent faults, a single test often shows everything working correctly. The starter spins on the bench, the solenoid engages, and you think you're done. Then two days later, the car won't start again.

Intermittent problems require repeated testing under different conditions. You need to check components when they're cold, after the engine has been running, and while wiggling connections. A single-pass test won't catch a corroded terminal that only loses contact at a certain temperature or a solenoid plunger that sticks once out of every ten cycles.

What tools do I need to test starter motor components intermittently?

You don't need a full professional shop, but a few specific tools make the job much more accurate:

Multimeter for checking voltage drop, resistance, and continuity across circuits
Test light a quick way to confirm power is reaching the starter solenoid
Jumper wires to bypass the ignition switch and test the starter directly
Remote starter switch lets you activate the starter from under the hood safely
Battery load tester to rule out a weak battery that mimics starter problems

If you need to order these as a set, you can get a starter motor test kit online without hunting for individual pieces.

How do I test the starter motor when the problem only happens sometimes?

The key is to simulate the conditions where the failure occurs. Here's a step-by-step approach that covers what a good video demonstration would show you:

Check the battery first. A battery with low cranking amps can mimic a starter problem. Load test it and make sure it reads above 12.4V at rest.
Perform a voltage drop test on the positive cable. Connect your multimeter leads to the battery positive terminal and the starter solenoid input. Crank the engine. You should see less than 0.5V drop. Anything higher points to a bad cable or connection.
Test the ground side the same way. Measure between the starter housing and the battery negative terminal during cranking. Again, anything over 0.5V indicates a grounding problem.
Activate the solenoid directly. Use a jumper wire from the battery positive to the solenoid trigger terminal. If the solenoid clicks and the motor spins every time, the problem is likely upstream in the ignition switch, relay, or neutral safety switch.
Repeat each test multiple times. This is the part most people skip. Run each test at least five to ten times. Wiggle wires while testing. Heat the solenoid with a heat gun and test again. Tap the starter housing lightly with a rubber mallet between tests.

For beginners who want a more guided look at this process, this beginner's guide to troubleshooting intermittent starter problems covers the basics in more detail.

What are the most common mistakes people make?

Several habits lead people down the wrong path when chasing intermittent starter issues:

Testing only once. If you test the starter once and it works, you haven't ruled anything out. Intermittent means it fails sometimes, so you need to test repeatedly.
Ignoring the wiring. Most intermittent starter problems aren't inside the starter itself. Corroded terminals, cracked cable insulation, and loose ground straps cause more failures than bad armatures or worn brushes.
Skipping the solenoid. The solenoid is a separate component that can fail independently. A sticking plunger or burned contacts inside the solenoid will cause exactly the kind of hit-or-miss behavior you're chasing.
Replacing the whole starter without diagnosing. Swapping in a new starter fixes the problem sometimes, but if the real issue was a bad ground or a failing ignition switch, the new starter will have the same symptoms.
Not checking under load. A wire can show perfect continuity on a meter but fail when 100+ amps flow through it during cranking. Voltage drop testing under load is the reliable method here.

How do I know if it's the starter motor or something else?

This is where systematic testing saves you time and money. Here's how to narrow it down:

If you hear a single loud click but no cranking the solenoid is likely getting power but the starter motor isn't spinning. Could be a bad solenoid contact, worn brushes, or a dead spot on the armature.
If you hear nothing at all check for power at the solenoid trigger wire. No power there means the problem is in the ignition switch, starter relay, neutral safety switch, or the wiring between them.
If the starter spins but doesn't engage the flywheel the drive gear (bendix) may be worn or sticking. This is a mechanical failure inside the starter.
If it works fine when cold but fails when hot heat soak is likely expanding a cracked solder joint or a worn bushing inside the solenoid. Test it after the engine has been running for 20 minutes.

Can I fix an intermittent starter problem myself?

It depends on what you find. If the issue is a corroded terminal or a loose ground bolt, that's a straightforward fix clean the connection, tighten the bolt, and apply dielectric grease. Replacing a starter relay or neutral safety switch is also within reach for most home mechanics.

If the solenoid contacts or starter brushes are worn, some starters allow you to replace those components separately. Others require a full starter replacement. If you're not comfortable disassembling a starter motor, buying a remanufactured unit is a practical option.

What should I do after I find the problem?

Once you've identified the failing component, replace it and then retest the entire starting circuit. Don't just assume the fix worked run the same intermittent testing process again. Start the engine ten or fifteen times over a few days. Check voltage drops on the repaired connection. Make sure the fix holds up under the same conditions that caused the original failure.

Keep a record of what you tested, what readings you got, and what you replaced. If the problem comes back, that record will save you from repeating the same diagnostic steps.

Quick diagnostic checklist

Battery voltage at rest is above 12.4V
Battery passes a load test
Positive cable voltage drop is under 0.5V during cranking
Ground cable voltage drop is under 0.5V during cranking
Solenoid clicks and engages when triggered directly with a jumper wire
Starter motor spins consistently across at least five consecutive tests
All tests repeated with engine hot and with wire harness wiggled
No intermittent failures observed after repair over multiple start cycles

Tip: If every test passes and the problem still returns, have the starter armature tested for dead spots at an auto parts store or shop with a growler tester. That's the one failure mode that's nearly impossible to catch with a multimeter alone.