FREE Starter & Alternator Testing at O’Reilly Auto Parts

An alternator is designed to provide continuous power to the various electrical systems in your car, including the radio, lighting, instrument panel, and more. Secondarily, it also ensures the battery is kept healthy and fully-charged. The alternator and battery work together to seamlessly provide the exact input energy needed to keep all the systems in your vehicle working as they should. When the engine is running, the alternator also provides the power needed to deliver spark and keep your engine running. Located at the front (or side) of your engine, your alternator is spun by the serpentine belt, which is powered by the crankshaft. The alternator turns this mechanical energy into electrical power to charge the battery so it can be started once the engine has been turned off. Alternators produce alternating current (AC) power, which is converted to direct current (DC) power by an internal rectifier. This is necessary because your vehicle's electrical system is not designed to use AC power, so this conversion inside the alternator supplies appropriate voltage to power the electronics. Newer alternators may also be designed with a larger capacity to support modern electrical amenities such as power windows, navigation units, infotainment systems, and heated seats. Since an alternator is such a crucial part of your charging system, it’s important to pay attention to signs of alternator failure to help keep your vehicle running as it should.

Do Alternators Charge Batteries?

The electrical systems in your car are closely intertwined and depend on one another for power, and your alternator helps charge the battery by supplying direct current (DC). But conversely, the alternator is not intended to be a battery charger, per se. Your alternator is only meant to restore charge to the battery that was used when you started your engine, or if you used electrical accessories while the engine wasn't running. If the battery is extremely discharged or dead and you have to jump start your vehicle, it causes the alternator to have to work harder to get the battery back to a full charge, which can result in excessive heat and could cause the alternator’s electronics or bearings to fail. This can include damage to the internal diodes, solder connections, and can even liquefy bearing grease and prevent it from protecting the alternator’s bearings. Restoring a complete charge to a battery that is at 50% charge using only your alternator can take up to 11 hours of driving to bring the battery up to 90% or more, and during that entire duration the alternator must run at peak output which generates a great deal of heat.

If your battery is completely dead or extremely discharged, it's usually better to plan to recharge your battery fully using a battery charger. For this same reason, if your battery is failing to hold a full charge or is failing and you don't replace it in a timely manner, it is very possible that the alternator could also fail. If your car consistently suffers from a dead battery when parked overnight or for a couple of days, it could indicate a parasitic drain that should be addressed to reduce the risk of battery and alternator damage. Keeping your entire charging system working as it should can help to ensure that each component in the system lasts as long as possible. If you need to have your battery recharged and don’t have your own battery charger, visit your local O’Reilly Auto Parts. We not only test batteries for free, but can also place them on our in-store trickle charger to safely bring them back to a full charge.

Why Do Alternators Fail?

While most alternators are designed to last anywhere from 40,000 to 100,000 miles, they can wear out and fail internally over their life. The lifespan of your vehicle’s alternator can be affected by a number of variables, many of which are not within your control. Environmental conditions and high temperatures, debris and breakdown of moving components, or a buildup of contaminants can cause parts of an alternator to wear out and eventually fail. Electronic components may also suffer damage due to moisture, or your alternator may be overworked attempting to charge a failing battery.

• Damaged Alternator Bearing

  A common cause of alternator malfunction is a bad alternator bearing, which is designed to reduce friction while the pulley spins. With constant heat, stress, and friction, an alternator bearing can wear and may no longer spin as freely. A bad alternator bearing can make it harder for the engine to turn the alternator and limit the amount of power generated, which can prevent your battery from being recharged. This can also cause extra stress on the alternator, belt, and engine. In extreme circumstances, the alternator bearing may lock up and lead to belt noise and damage, eventually causing the belt to snap and resulting in other symptoms like overheating, loss of power steering, air conditioning, and more.

• Fluid Leak

  A dead alternator could also be caused by a fluid leak from the engine or power steering system. Oil leaks from the engine or the power steering hoses or pump can drip into the alternator, coating the internal components with oil and limiting conductivity. This can damage the mechanical and electrical charging components of the alternator, causing it to fail or no longer produce adequate power to recharge the battery or keep the engine running. Coolant, power steering fluid, or oil intrusion from leaking valve cover gaskets, or an alternator located below the oil filler neck, could cause the composite alternator brushes which maintain electrical contact inside the alternator to turn to paste and no longer produce power.

• Using Jumper Cables Incorrectly

  Another reason for alternator failure is the incorrect use of jumper cables. When jump-starting a car, it’s important to connect each cable on both batteries to the appropriate terminals to avoid reversing the polarity. Crossing or hooking up the cables backwards can damage your alternator and battery, as reversing the polarity for even a moment can cause voltage spikes, sparks, and damage to the fusible link that may be installed in the alternator, as well as any external regulators and, in some cases, the engine control unit (ECU). Need guidance on jumping a car? Read our helpful article on how to jump-start a car battery to prevent damaging your vehicle.

• Personal Driving Habits

  If you are a driver that loves to use their vehicle’s electronic accessories while idling, this can unfortunately put a strain on the alternator and impact its lifespan with time. Though this is rare, alternators typically work best above 1650 RPMs, so limiting the time spent using high-load accessories like lights, blower fans, radios, and more at idle can reduce the risk of alternator failure. A number of modern vehicles also use the engine control unit (ECU) which externally regulates the alternator’s output. This allows the alternator to only generate power when RPMs are above a set threshold to reduce the burden on the engine and increase fuel efficiency at idle.

What Are the Signs of a Bad Alternator?

If your car won’t start or run as it should, you may want to check your alternator to make sure your electrical system is performing as at its intended level. Your alternator helps maintain the battery’s charge and supplies the vehicle with power. To keep up with electrical demand, your alternator needs to produce between 13.5 to 14.8 volts when the engine is running.

Signs of a bad alternator include your car not turning over or starting, a dead battery, or an illuminated battery warning light that may indicate the alternator is not adequately charging the battery. Dim or excessively bright headlights, or headlights that get brighter as engine RPM rises, may be another sign that the alternator is not working at its best. You may even notice a burning rubber smell due to the alternator’s overworked wiring or serpentine belt abrasion. Additionally, the sounds of a bad alternator include whining, squalling, screeching, clicking, or scraping noises during startup, or a rattling sound that could point to a loose needle bearing.

Another reason for alternator failure is a bad voltage regulator. Voltage regulators on some vehicles are built into the alternator, meaning that when they fail, the entire unit needs to be replaced. Many modern vehicles also have alternators that are externally-regulated by the ECU, which allows the control unit or module to dictate the alternator’s output. Voltage regulators meter the amount of power sent from the alternator to the rest of the electrical system to ensure that the maximum voltage is not exceeded. When the voltage regulator fails, it can supply too much or too little voltage, causing performance issues or electrical damage. Symptoms of a bad voltage regulator include a stalling engine, a car that dies while running, an illuminated Check Engine or battery warning light, flickering headlights or headlight intensity that rises and falls with the engine RPMs, or a spike in voltage which can overcharge the battery or damage electronics. An overcharging battery could result in evaporation of water from the battery case, which could also cause the battery to smoke or smell like sulfur. You can use a multimeter to measure the voltage at your battery terminals. If the voltage is above 14.7 volts or below 13.7 volts when the engine is running, it may indicate a failing alternator or voltage regulator.

It’s important to replace or repair a dying alternator as soon as possible. Your vehicle’s performance can dramatically decrease when an alternator fails, affecting your ability to start and safely drive your car. You may also save yourself the cost of replacing a battery if you repair or replace your alternator as soon as you notice any failure symptoms. Whether it’s using alternator repair kits to get your alternator back to normal or installing a replacement alternator, fixing a malfunctioning or underperforming alternator can restore the performance you expect from your vehicle’s charging system.

A starter is an electric motor that works to convert electrical energy into mechanical energy to start your vehicle. Powered by the battery, a starter motor is engaged when the ignition switch is turned to the Start position, and turns over the engine by engaging the geared flywheel or flexplate and spinning the crankshaft. The starter solenoid, which is often mounted to the starter itself, receives the signal from the ignition switch to connect battery voltage to the starter, extend and spin the starter gear, and then retract the shaft and gear when the engine has started. Unlike an alternator that is constantly working while the engine is running, starters disengage once the engine has started and the key is returned to the run position to prevent damage to the flywheel or starter gear.

Why Do Starters Fail?

Problems with your vehicle’s starter can be caused by normal wear and tear, or may point to a larger issue with the starting system, and it’s important to understand why starters go bad. Often, starters simply fail due to demanding conditions, heat, and prolonged use, although there can be a few other variables that lead to starter failure.

• Bad Starter Solenoid or Relay

  The starter solenoid is located outside the starter’s casing, and allows electricity to move from the battery to the starter temporarily to start your vehicle. Because of its location, a starter solenoid is exposed to extremely hot temperatures, which can cause mechanical failure, sticking, and arcing. A failed starter solenoid can cause smoke, or it may fail in the extended position and cause starter gear or flywheel damage. When a starter solenoid fails, it is often necessary to replace the starter and solenoid as a unit, as the solenoid may not be serviceable separately. The starter relay works similarly to a starter solenoid, but can be replaced separately if it has failed. Starter relays are typically installed in the fuse box located in the engine compartment.

• Worn Internal Windings

  Your starter motor has internal windings that are made to engage the starter shaft and gear, and crank the engine. Due to heat and prolonged use, these windings can wear out, causing the gear to not extend, not spin, or both. Bad internal starter windings can cause the engine not to start, and may create a clunking or clicking sound if the starter gear extends but does not have enough torque to spin. If you’ve experienced these symptoms, the starter may need to be replaced. Getting your starter bench-tested can help you define the issue, which can identify whether the problem is with the starter or another external component.

• Pinion Gear Teeth Wear

  The pinion gear’s teeth connect to the flywheel or flexplate when the starter is engaged, and the metal teeth can experience wear or damage over time. This is especially true if the starter is engaged when the engine is already running. If the teeth have been damaged, the starter gear may fail to correctly mesh with the gears of the flywheel or flexplate, and the starter may make whirring noises without cranking the engine. Missing or worn teeth may also cause a grinding sound on startup, and can be further exacerbated by continued engine cranking. It may be necessary to remove the starter to inspect the teeth of both the pinion gear and the flywheel or flexplate for signs of wear or damage.

• Incorrect Starter Installation

  Some issues with your starter can be attributed to incorrect starter installation. The bolts that secure your starter to the engine also help create the ground necessary for adequate current flow. Loose bolts can create electrical contact problems, and some starters may require specific shims or spacers that maintain appropriate starter alignment. If this hardware is not used, it could cause damage to the flywheel and starter. Loose bolts can also cause physical contact issues between the starter gear and the flywheel if the starter assembly is not secured properly. On the other hand, over-tightened bolts can also cause the starter housing to crack, which may allow for starter movement and throw off its alignment. It is important to check your service manual to determine the correct torque specifications for the starter and electrical terminal nuts. In many cases, the bolts extend through a non-conductive material that can crack if the terminals are over-tightened, allowing power to arc and not reach the starter.

Your starter is one of the most important parts of your engine, and is put under significant stress throughout its life. Starter failure is common due to demanding conditions, and a bad starter will typically exhibit a few symptoms before it dies completely. The most common sign that your starter is dying is that the engine won’t turn over when you turn the key or press the ‘Start’ button. This could also be caused by a dead battery, or may point to an issue with the starter, ignition system, or other electrical components. Over-cranking a starter generates a great deal of heat and can potentially shorten the life of the starter motor. Some common reasons over-cranking occurs is insufficient fuel or fuel pressure for combustion, camshaft and crankshaft sensors that are out of specification or providing inaccurate timing or firing information to the engine control unit, poor air and fuel mixture due to a clogged or dirty mass air flow (MAF) sensor, and other factors.

• Vehicle Won’t Start & Makes Clicking Noises

  If you turn the key and hear your starter “click”, this is often a sign that the starter gear is engaging but the starter or battery does not have sufficient power to turn the engine over. It is important to ensure that your battery is fully charged and has appropriate cranking voltage to activate the starter. In other cases, the starter may not click but you will be able to hear it spin. If that is the case, the internal windings of the starter may be worn and no longer engaging the gear, but can still spin the starter because it is not under a load or the solenoid is not extending the starter shaft, or bendix, to engage and turn the flywheel.

• Grinding or Whirring While Starting Your Engine

  Other noises on startup, such as grinding and whirring, may be a result of misaligned, worn, or failing starter components. Continuing to try to start your vehicle despite these sounds can cause further damage not only to the starter components, but also to the flywheel, making a small problem worse. It is also considerably more expensive and time-consuming to repair a ring gear than a starter. If your battery warning light is illuminated, try testing the battery to see if it’s supplying enough power for the starter, or you can try using jumper cables and another battery to test the starter and battery.

• Smoke Coming From Starter

  One last symptom of a bad starter is the presence of smoke during startup, which can be caused by the starter overheating. Smoke can be attributed to an electrical short, a blown fuse, a bad starter solenoid, or an issue with the ignition switch. The starter should be inspected and repaired or replaced as soon as possible to prevent further damage. You can reduce the cost of replacing a starter by performing a DIY starter repair with the right parts, tools, and accessories from O’Reilly Auto Parts to keep your vehicle starting reliably.

Get Free Starter & Alternator Testing at O’Reilly

Ready to test your vehicles’ starter or alternator, but unsure where to start your diagnosis? It’s as easy as driving to an O’Reilly location near you. Our experienced parts professionals can test your starter or alternator while it’s still on your vehicle. If your vehicle won’t start and you believe the starter or alternator may be the culprit, simply bring the part to an O’Reilly Auto Parts store near you and we would be happy to bench test it for you. Our specialized testing equipment allows the part to be tested securely and provide quick and accurate results to determine if your starter or alternator has failed or is performing outside of specification. We also carry top-of-the-line replacement starters, alternators, voltage regulators, starter relays, solenoids, and more charging and starting system components to help you complete your repairs right the first time.

Missing a tool you might only need once? Ask about our free Loaner Tool Program, where you can rent a specialized tool for a deposit, and get your money back once it’s returned. Find the starting system parts your vehicle needs to run its best at a nearby O’Reilly Auto Parts location.

O’Reilly Auto Parts’ FREE Store Services

Along with free starter and alternator testing, O’Reilly Auto Parts also provides several other free store services, including free Check Engine light testing, wiper blade installation, headlight bulb installation, battery testing, and fluid and battery recycling. Stop by a local O’Reilly Auto Parts store and chat with one of our knowledgeable parts professionals to learn more about our free store services.

Testing your vehicle’s starter motor can help you diagnose starting problems and save time and money on unnecessary repairs. While you can test your starter motor yourself, this DIY job can be dangerous to perform at home. To properly test the starter, the starter motor needs to be secured, as it has to spin at a high operating speed. The torque and speed at which your vehicle’s starter operates can be hazardous to test without the right tools and safety equipment. To be safe and ensure the test is done properly, bring your car, or just the starter, to O’Reilly Auto Parts. Our parts professionals can clamp the starter motor in place with equipment designed specifically for starting testing to complete the test safely and quickly. Starter testing at your local O’Reilly Auto Parts store is free, and can be completed at any of our more than 6,000 locations. If the test determines you need a replacement starter motor, we can also help you find the right parts and tools to help you complete your repair.

Get Free Starter & Alternator Testing at O’Reilly

Ready to test your vehicles’ starter or alternator, but unsure where to start your diagnosis? It’s as easy as driving to an O’Reilly location near you. Our experienced parts professionals can test your starter or alternator while it’s still on your vehicle. Visit any O'Reilly Auto Parts store and ask about our free starter and alternator testing. One of our parts professionals can test your vehicle's alternator in the parking lot. If your vehicle won’t start and you believe the starter or alternator may be the culprit, simply bring the part to an O’Reilly Auto Parts store near you and we would be happy to bench test it for you. Our specialized testing equipment allows the part to be tested securely and provide quick and accurate results to determine if your starter or alternator has failed or is performing outside of specification. We also carry top-of-the-line replacement starters, alternators, voltage regulators, starter relays, solenoids, and more charging and starting system components to help you complete your repairs right the first time.

Missing a tool you might only need once? Ask about our free Loaner Tool Program, where you can rent a specialized tool for a deposit, and get your money back once it’s returned. Find the starting system parts your vehicle needs to run its best at a nearby O’Reilly Auto Parts location.

O’Reilly Auto Parts’ FREE Store Services

Along with free starter and alternator testing, O’Reilly Auto Parts also provides several other free store services, including free Check Engine light testing, wiper blade installation, headlight bulb installation, battery testing, and fluid and battery recycling. Stop by a local O’Reilly Auto Parts store and chat with one of our knowledgeable parts professionals to learn more about our free store services.