Starters VS. Alternators

Ask someone the difference between a starter and alternator, and he/she may look at you like you are crazy. After all, they are the same component, right? Wrong. While they are both integral parts of a vehicle’s electrical system, they perform different tasks. The job of the starter is to do just that: start the engine; while the alternator is the electrical force used to charge the battery – like your cell phone charger – and provide power when the engine is running.

Even though they are different parts, there remains confusion over these two electrical components. What is even more confusing is how you know when your starter is failing as opposed to your alternator. Keep reading to learn the signs of failing starters and alternators in heavy-duty trucks and how to test each one.

Is My Starter Failing?

Whining noises, burning smells coming from the engine and lights illuminating but no action are just some of the symptoms of a failing starter; however, the most common sign of a dying starter in heavy trucks is when the engine won’t turn over quickly or at all. In this instance, you will hear a clicking noise when you go to start the engine. Smoke is also a warning sign – possibly because the starter was operating too long without breaks.

Starters have a life expectancy of approximately seven years, or 100,000-150,000 miles; and if you are approaching this timeframe with your starter, it may be a good idea to inspect and replace it. If nothing happens when you start the engine, your starter has already gone bad.

How To Test My Truck Starter?

Grab a voltmeter from your local hardware store and begin checking your battery and starter. The voltmeter will have a red and black wire. Take the red lead on the voltmeter and draw it to the positive terminal on the starter while placing the black lead to the negative terminal on the starter. If the starter gear comes out but does not spin rapidly, chances are you have a failing starter.

Is My Alternator Failing?

When an alternator is dying you will notice similar warning signs as the starter. Dimming and flickering lights is just one warning sign of a dying alternator; however, drivers may experience these symptoms:

  • Weak or dead battery;
  • The battery warning light is on;
  • Whining, squealing or grinding noises;
  • Engine cranks slowly and makes clicking noise;
  • Engine completely stalls.

Alternators have the same lifespan as starters. When replacing batteries and starters in vehicles, it is best to replace the alternator, as well.

How To Test My Truck Alternator?


Test 1) Grab your voltmeter, again. This time get a friend to help you test your alternator by getting him/her to start the vehicle’s engine and rev it up to 1500 RPMs. The voltmeter should read between 13.3-14.2 volts; but if it stays consistent or drops in voltage, then you could have a dying alternator.

Test 2) With the engine still running, have your friend turn on the headlights. If you see the voltage drop again on the voltmeter, it is time for a replacement.

Where To Buy Replacement Starters and Alternators?

Call us bias, but Match Made has some of the best OEM starters and alternators that are a perfect fit for all types of fleet vehicles. Complete with a two-year warranty, these aftermarket truck parts are affordable and easy to install.