Why Would a Starter Motor Burn Up?

There are multiple reasons for a starter motor’s malfunctioning, from corroded connections and overheated to other common causes that we will dive into below. Hearing the dreaded clicking sound or grinding noise means there is something wrong with your car. Understanding the reasons for a burnt out starter motor can help you prevent it from happening in the first place.

Ignition Switch

Car starters engage when you turn the key in the ignition mechanism. Inside the ignition mechanism is a cylinder, which can get stuck. If this happens, then the starter will not disengage as it is supposed to once the engine has started. The starter is not meant to stay engaged after the engine has started, so this causes the starter to burn out.

If you have a sticking ignition switch that is sending a constant feed to the starter, you may hear a kind of whirring or high pitched ringing sound, followed by an overheating or burning smell that indicates starter burnout as well.

Insufficient Battery Voltage

Raise the hood of the car and check the car battery voltage using a voltage meter while the car is off. The red probe goes on the positive terminal and the black one goes on the negative terminal. A fully charged battery needs to come in at 12.5 to 12.8 volts. Anything less could mean that your battery is not strong enough to power the starter. If the battery is bad, move to the next step.

Shorts/Wiring

The starter connects to the battery to operate once the key is turned in the ignition. Sometimes there is a short in the wiring that connects these components, which can cause the starter to receive a current from the battery even if the ignition is turned off. Once again, because the starter is not meant to stay continually engaged, this burns out the starter. In addition, a poorly charged battery can cause starter burnout because the starter will try to operate on less than optimal charge, which can stress the parts of the starter.

Solenoid

Some cars have a solenoid attached to the starter. Specifically, a lever from the solenoid is connected to the starter's clutch and pinion assembly. If the solenoid switch stays engaged, then it continues to pull on the clutch and pinion assembly and will wear out the starter.

User Error

A starter is meant to engage only long enough to turn the flywheel and crank the engine. If a driver turns the ignition key for longer than this takes, the starter motor is forced to continue operating. Although doing this once or twice won't burn out the starter, doing it repeatedly could do damage.

Defects

Although fairly uncommon, some cars are just equipped with bad starters. Some starters have manufacturing defects that cause them to work improperly, leading to starter motor failure. The defects can range anywhere from poor connections to bad parts within the starter motor itself. If your starter is replaced but burns out within days, and no one has been starting the vehicle differently than before, you can suspect the burnout was due to a manufacturing problem rather than an ignition, wiring or solenoid issue.

Other Issues

A dirty engine is full of dirt and grime, as well as corrosion from the oxidation of metal components. If this dirt and grime get into the starter, it can act like sandpaper and cause component damage and burnout. The dirt and grime, in addition to the corrosion, can hinder the electrical current from the battery to the starter motor. The low voltage received by the starter stresses it. Incorrect starter fluid levels also stress the starter because the pressure in the system is incorrect. You can prevent these engines through routine maintenance checks and cleaning.

Replace the Starter

If your starter burns out, it’s time to remove the worn-out starter and install a replacement starter.

Jack the car up on the driver's side using the jack and place a jack stand under the frame near the jacking point. Raise the jack stand up to the frame of the car.

Crawl under the car and find the starter. It's near the transmission and looks like a round canister with electrical wires coming from it. Mark the electrical wires using a marker and masking tape, noting the proper location of each one. Disconnect the shift control cable from the transmission by manipulating it and unhooking it. Remove the speedometer cable, using a wrench to loosen it.

Disconnect the electrical wires from the starter using a wrench to remove the nuts. Unplug the wiring harness, and then remove the mounting bolts from the starter using a ratchet and socket. Pull the starter away from the engine.

Put the new starter on the engine and tighten the mounting bolts with the socket and ratchet. Reconnect the electrical wires, tighten the nuts with the wrench, and then plug in the wiring harness.

Reconnect the speedometer cable to the transmission and tighten it with a wrench. Reconnect the shift cable by hooking it back into the lever. Remove the jack stand from under the car.

Lower the car back to the ground and reconnect the negative battery cable. Tighten the nut with a wrench and then start the car to test the installation.

Video demonstrating how to replace a starter:

Comments on this video:

• Good video, the older starter with heavy duty brushes are more reliable then the newer replacement starters. I have also never burnt out starters and on diesels on cold days we cranked our tractors for long times with extra batteries on a trolley when we ran out of ether.
• Cool! Thanks for posting. Never knew starters (well this one anyways!) were so robust! The heat and increase in resistance snowball effect rings true. Voltage goes down, amps try to satisfy E=I×R by increasing and wires and motor and connections get good and toasty!