When does the starter motor need to be replaced?

The starter motor in a car is a heavy-duty electric DC (Direct Current) motor. It is bolted to the engine or transmission and is powered by the 12-volt battery. The starter motor's job is to turn over the engine when you want to start it.

If the car doesn't start, does it mean that the starter motor is bad? Not always, a bad starter motor is only one of the possible causes; read how the starting system works below. The starter motor may stop working suddenly, or it may fail gradually.

What are the signs that the starter motor is going bad?

• The engine won't turn over on the first attempt; The failing starter may click but won't turn over on the first try. It may take several tries to make it work.
• At times a worn-out starter motor won't work when the engine is hot, but starts working again after the engine cools down.
• When starting, the engine turns over slower than usual even though the battery is good.
• The starter motor sounds 'strained' when turning over the engine and possibly produces an abnormal grinding sound.
• When the overrunning clutch of the starter motor fails, you can hear the starter motor runs, but it fails to turn over the engine, or turns it over after several attempts.
• When the starter gear fails to engage with the engine flexplate or flywheel gear when starting, you may hear a loud screeching noise, but the engine will not turn over. This could happen due to a bad starter motor or worn out flexplate/flywheel gear.
• One of the main fuses protecting the starter motor circuit burns out when starting the engine due to excessively high current drawn by a worn-out or shorted starter motor.
• Tapping the starter motor makes it work when it's worn out and fails to operate.

How do mechanics check a starter motor?

In the old days, the trick was to tap the starter motor lightly with a small hammer and see if it starts working after that. If it did, the mechanic knew the starter motor was bad. Today, mechanics simply measure the voltage at the starter motor terminals.

A starter motor has two wires connected to it: a small wire for the control circuit and a larger cable that is connected to the positive battery terminal (see the diagram below). If there is a battery voltage at both starter terminals when pressing the Start button or turning the key and the starter motor doesn't run, it's bad and needs to be replaced.

Why does the starter motor fail?

It has several moving and rotating parts inside. Over time, things like electric carbon brushes, bearings or an overrunning clutch wear out.
The electrical contact points inside the starter solenoid can also become pitted or burned. What is the symptom of bad contacts inside the starter solenoid? When attempting to start the car, you will hear a single click from the the starter solenoid, but the engine would not turn over even if the battery, cables and the cable terminals are good.

How long does the starter motor last?

On average, a starter motor lasts for 100,000-150,000 miles. In many cars, the starter motor lasts for the lifetime of the vehicle; however in some cars, it can fail prematurely.

How much does it cost to replace a starter motor?

In an average front-wheel drive car like Honda Accord or Toyota Corolla with a 4-cylinder engine, the labor charge to replace a starter motor varies between $95 and $175. In some vehicles with larger engines (e.g. BMW, Cadillac Northstar V8, Toyota V8), an intake manifold or other parts must be removed to get to the starter motor and that will require more labor ($260-$450).

An aftermarket starter motor (part) costs $85-$220 plus the core charge. Many part stores will refund you the core charge if you return the old starter motor (core).
An original (OEM) starter motor is more expensive ($270-$480).
For example, one of our friends decided to replace the starter motor in his 2014 Honda Accord. He said that once in a while it would take a few tries for a car to start and that the problem was getting worse. He paid $390 for an original part plus $127 labor at the dealership.

Can a starter motor be rebuilt? Yes, a local auto electric (Starter & Alternator shop) should be able to rebuild the starter motor. Prices range from $65 to $150 (not including installation). Of course, rebuilding a starter motor takes more time.

If the starter motor gear does not mesh properly with the flexplate ring gear, the starter motor may produce a loud grinding or screeching noise when attempting to start. In this case, both the starter motor and the flexplate (or flywheel in a manual transmission) ring gear must be inspected. Besides a bad starter motor, this could be caused by worn-out flexplate or flywheel gear teeth. Replacing the flexplate or flywheel is more expensive, as in either case, the transmission must be removed.