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Stop/Start Alternators

Counterman
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Counterman

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Here’s the scenario: A customer comes into your store looking for an alternator for their vehicle. You look up the year, make and model and you see an application note on the screen. It tells you to ask the customer whether or not the vehicle is equipped with stop/start technology.

As with many of the technological advancements from the past decade or two, stop/start came about thanks to the need to meet ever-tightening emissions and fuel-economy standards. In the late 1990s to early 2000s, hybrid vehicles were on the rise. These vehicles could propel themselves purely on electric drive, then start the engine as needed
based on driving conditions and driver input.

The problem was that traditional starters weren’t up to the task. They cranked the engine over too slowly, and the process was rather jarring. So, reinforced starter motors and flexplates were designed to combat this issue.

Over time, automakers started to include stop/start systems in more and more vehicles. This is largely due to the fact that it was a simple way for OEMs to reduce carbon emissions from their entire lineup, and they receive certain incentives (or avoid costly penalties) for accomplishing this goal.

Engines today are far more fuel-efficient than those that came before them, but automakers still need to squeeze everything they can from every drop of fuel. Or, in this case, they’re trying to reduce how much fuel is wasted during everyday driving. In an urban environment, vehicles can end up sitting at idle up to 35% of the time. The energy from burning fuel at idle is wasted since the vehicle isn’t in motion, but the vehicle still is producing harmful emissions.

With the ability to stop and start the engine as needed, automakers are able to reduce the carbon footprint of their entire lineup. To you and me, it might not seem like much can be gained by stop/start technology. But, when you think about the number of vehicles on the road today, you can see the benefit a bit more clearly. It’s estimated that stop/start systems can reduce CO2 emissions by up to 10%, and maybe slightly more depending on conditions.

The engine stops whenever the vehicle comes to a stop, then restarts immediately as soon as the driver transitions from the brake pedal to the throttle. Most stop/start systems crank the engine over at a higher RPM when compared to the initial cranking speed. This helps to make the process less jarring and less noticeable to drivers and passengers alike.

Is a Stop/Start Alternator Different?

The short answer is yes, but how so varies from one automaker to the next. Many modern-day alternators will have some sort of integrated control module on board. However, a stop/start alternator may be responsible for starting the engine as well as recharging the battery. This unit is commonly referred to as a starter/alternator.

A starter-alternator is used by the PCM to crank the engine via the belt drive. The belt may contain more teeth (the belt may be wider) due to the load and stress applied while cranking. Starter-alternators boast faster engine startup than traditional starters, and they can do it without making as much noise or vibration. The traditional starter will crank the engine for the initial startup, then the starter/alternator will handle all of the restarts until the next driving cycle.

How long does a traditional alternator typically last? In most cases, one could expect an alternator to last for 90,000 to 120,000 miles, maybe more. A stop/start alternator should see a similar life expectancy. If the alternator fails within 10,000 to 20,000 miles, there might be another issue that’s causing the premature failure. This could include a bad battery; wiring issues (loose connections, corrosion, intermittent shorting, etc.); overload from non-factory electronics; and/or a faulty voltage regulator (though these days this is usually integrated into the alternator).

Tips and Tricks

Stop/start might not be very popular among consumers, but this technology has led to multiple innovations and changes across the industry. For example, electric air-conditioning compressors and water pumps have been developed so that they can operate while the engine is off.

So, what should you tell your customer if they’re replacing a stop/start alternator? Try to make sure they’re repairing the problem – not just a symptom – and sell them the complete repair. If their vehicle has a starter/alternator, they should be inspecting the condition of the entire belt drive. This includes the pulleys, the belt and especially the tensioner. If the belt isn’t tensioned properly, they could experience a number of symptoms, including noises, improper charging voltage, intermittent cranking issues and more.

Don’t forget about the battery and cables! Always replace the battery with one that’s comparable to the OE-specified unit. The main battery typically is either an absorbent glass mat (AGM) or an enhanced flooded battery (EFB). These batteries are more advanced, and better able to support the increased number of charging cycles and additional load placed on the system by the stop/start features. Clean all electrical connections and protect them if necessary to prevent future corrosion.

As always, it’s best practice to reference the OEM service information whenever servicing the alternator on a stop/start vehicle. Always respect the OEM’s recommendations when it comes to specific tooling, torque specifications and tightening sequences. Whenever possible, connect a scan tool to the vehicle and look for fault codes. A scan tool that’s capable of bi-directional communication might be required to reset the battery-recognition or battery-life monitor. CM

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    • Counterman
      When Good Alternators Go Bad
      By Counterman
      When I hear good and bad in the same sentence, I think of the classic Clint Eastwood movie, “The Good, the Bad and the Ugly.”
      This isn’t the Old West, but I can draw a perfect parallel between the title and the fight we sometimes have with alternators.
      When they’re good, they’re good. When they’re bad, they’re bad. So, what’s the ugly? That’s when they’re good, but we think they’re bad because there’s an electrical problem that prevents them from working properly. It gets even uglier when the problem is hard to find, and probably the ugliest when a good alternator is called bad.
      What an alternator does is simple, or at least we’ll keep it that way for now. It outputs direct current (DC) to power vehicle electrical systems and maintain and recharge the vehicle battery. An alternator is aptly named because it generates an alternating current (AC), which is, in turn, converted to DC.
      We can divide the alternator into two different systems: the mechanical and the electrical. On the electrical side, you have the components that are responsible for generating and managing the electrical current, which include the rotor, stator, regulator and rectifier. The rotor and stator are the main components that generate electricity, based on fundamental electromagnetic principals. The regulator is what controls the output of the alternator, and the rectifier is what converts AC to DC.
      The Good
      When an alternator is good, alternating current is being generated by the rotor and stator, the rectifier is converting it to direct current and the regulator is controlling the output. If a problem develops with one of these, the result is either no voltage, too much voltage or an AC-voltage output. Any of those are bad.
      If this seems too simple, it is on purpose. We can get much deeper into it, which will make it more difficult, but the way we do things today has changed the process of diagnosing the charging system. Things were different years ago. We used to take alternators apart. We’d check the windings of the rotor and stator. Then we’d check the diodes in the rectifier, and finally check the regulator. As a matter of fact, regulators used to be separate from the alternator and they were mechanical devices compared to solid-state electronics. We’d take everything apart, check it all, determine what was bad and replace only what was needed.
      We don’t do that anymore. Alternators have been self-contained for many years. Regulators are built in. If an alternator isn’t working, we replace it. That’s it. We don’t think about why, nor do we even toy with the idea of taking it apart. Just send me a new one.
      On the mechanical side, you have the bearings that support the rotor, and the pulley that’s driven by the belt. If the bearings are bad, they’re loose or noisy. Pulleys used to be fixed chunks of metal. Now we see overrunning alternator pulleys (OAP) or overrunning alternator decouplers (OAD). When these go bad, they’re often noisy, or they may not spin the alternator.
      The brushes in an alternator are another mechanical part of it. They’re made of conductive materials that physically contact and rub against the slip rings. This is how the electrical current from the regulator flows into the rotor. But we don’t replace brushes anymore, nor do we replace bearings. We don’t even think about taking the alternator apart. We just replace it. The pulleys are the only parts we may replace separately.
      The Ugly
      When an alternator needs replaced, the process usually isn’t too difficult, but that’s when it can get ugly.
      As counter professionals, you deal with technicians, and you deal with do-it-yourselfers. Either way, when they ask for an alternator, you’re hoping the diagnosis is correct. The last thing you want is an alternator return. You might ask a few questions to see if they’ve done some basic diagnosis, but you’re in a tough spot. You don’t want to show disrespect, but you don’t want the original coming back covered in grease, because they found the “real” problem after they replaced it and it didn’t fix the problem.
      Do DIYers make mistakes? You bet. Do professional technicians make mistakes? We sure do. It’s not always easy, and diagnosis can be difficult. Any time electrical diagnosis is involved, the potential for mistakes can be greater, and charging systems are no exception. One problem is that alternator failure isn’t uncommon, and if the charging-system indicator is illuminated, that’s likely the problem.
      It’s easy to see the warning light, and even maybe check battery voltage with the engine running. If the battery voltage is at or below 12.6 volts, the alternator must be bad, right? After all, we would normally see 13.5 to 14.5 volts. This is what I like to call a reactive diagnosis. We react based on what we know is common and think that what we initially see tells the story. Sure, it’s possible that the alternator may be bad, but only possible. A fact of electrical diagnosis is that the majority of all electrical problems are caused by higher-than-normal resistance – in other words, a poor connection.
      Diagnostic Tips
      How, as technicians do we keep from making this mistake? We have to remember that electrical systems are far more complicated than they have been for years, and they require correct system voltage in order for all of the computers and electronics to work properly.
      Battery condition is critical, and a weak battery can prevent an alternator from properly charging. It’s also not unheard of to get a vehicle in that has both a bad alternator and a bad battery. It does happen.
      When diagnosing charging systems, an important detail not to overlook is performing a voltage-drop test on the battery and alternator cables. It’s safe to say that higher than normal resistance is responsible for the good majority of misdiagnosis and comebacks.
      The traditional tools we use for battery and charging-system diagnosis are a digital battery tester, a multimeter, a load tester and an amp clamp. However, for modern charging-system diagnosis, a scan tool has become a must-have. Modern charging systems are no longer stand-alone systems, with the vehicle ECM playing a large part in their control and operation.
      A power-management system is a more accurate name than charging system, and it includes the alternator, battery and ECM. These systems have been developed to improve fuel economy, battery life and alternator operation, and not only do they monitor battery condition, but some systems also can estimate battery condition as well. They control and adjust charging output and they also can perform diagnostics and set diagnostic trouble codes. Good alternators can go bad, but if you’re faced with answering questions and giving advice to your customers at the counter, make sure they’re covering all the bases of diagnosis, so a good alternator doesn’t turn ugly.
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