Blog Car Care Advice Charging System – How It Works, Parts, Problems
Car Care Advice

Charging System – How It Works, Parts, Problems

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What Makes up the Car Charging System? 

The charging system in a car provides electrical power for all of the vehicle’s operating needs. This includes charging the battery, firing the spark plugs during the combustion process, and powering the car’s electrical system. The electrical system runs throughout the vehicle, supplying power to the headlights and taillights, the heating and air conditioning systems, the infotainment system, the power accessories (locks, windows, seats, sunroof, etc.) the horn, the engine computer, and everything else in the car that depends on electricity to function. 

The primary elements of the charging system are the alternator, the battery, and the voltage regulator. These components are connected to each other and the other parts of the car’s electrical system by a complex wiring harness. 


What Does an Alternator Do? 

The alternator generates electricity to power your car’s electrical system. It is typically mounted to the outside of the engine and is connected to the engine’s crankshaft by a drive belt. The alternator converts the mechanical energy of your engine’s rotation into the electrical energy needed to run the vehicle. The alternator also recharges the battery, replacing the power that is used during the starting process (when the car relies on the battery alone).

What Are the Symptoms of a Bad Alternator? 

Without a properly functioning alternator, your battery will be unable to maintain its fully charged state. That can lead to a variety of symptoms of a bad alternator, which are listed below: 

The battery warning light comes on: While the battery light can indicate a battery-specific problem, it can also indicate a bad alternator. The alternator may be putting out voltage that is either too high or too low.  

How to fix it: Shut off the engine and check your owner’s manual for the location of the alternator and its drive belt. Proceeding with caution, open the hood and press down on the center of the belt, halfway between the alternator and the nearest pulley. If you can push the belt down more than a finger’s width, the belt may be loose. Also, check the belt’s alignment relative to the alternator. It’s always best to have a trusted mechanic take care of issues regarding your alternator and drive belt. If the belt is taut, the alternator may be bad and will need an alternator repair by a mechanic. If the belt is worn out, cracked, or otherwise damaged, it will need to be replaced. 

You hear whining noises: Since the alternator is powered by a drive belt and it rotates on a shaft supported by bearings, a problem with either of these items can cause a whining noise to come from the area of the alternator. 

How to fix it: Check the belt tension as detailed above and tighten or have it tightened by a mechanic. If it’s not the belt, the alternator should be checked by a mechanic. 

You smell burning wires or rubber: This is another indicator of either a bad drive belt, a bad alternator, or both. This can be caused by excess friction on the belt, failed components inside the alternator, or a combination of both. 

How to fix it: Once again, it’s either the belt, the alternator, or both. A mechanic can sort things out and make any necessary alternator repairs. 

Your car has trouble starting or stalls out while driving: Since your alternator charges the battery and fires the spark plugs in the engine, a poorly performing alternator will provide insufficient power for starting and driving.  

How to fix it: An alternator repair by a qualified mechanic is likely to be needed.  

Your car has a dead battery: Sometimes a dead battery is just a dead battery, but it can also be a symptom of a bad alternator. If the alternator is not putting out enough voltage, the battery will not be fully charged, and will eventually fail. 

How to fix it: A mechanic should check your alternator and charging system to make sure that the new battery will be fully charged and won’t fail prematurely.  

Your headlights are brighter or dimmer than normal: If your alternator is putting out the incorrect voltage (which can be either too high or too low), you may notice that your headlights appear too bright or too dim (or both), or even flicker as you drive.  

How to fix it: You will need a mechanic to make an alternator repair – as soon as possible! 

Your power accessories are not working properly: A bad alternator that is not putting out sufficient power can cause your power windows and seats to operate slowly, or you might lose power to items like your car stereo and interior lights. 

How to fix it: An alternator repair by a qualified mechanic should get you back on the road. 

What Does it Cost to Replace an Alternator? 

The cost of an alternator repair depends on several factors: 

If we look at all these factors on a spectrum, the lowest possible alternator repair cost will come from using a remanufactured alternator for a mass-market car that offers an easy installation and is done by a AutoNation Mobile Service technician. The highest possible alternator repair cost will be found by using a new alternator on a luxury-brand car that is difficult to install and is done by a dealer. While you have no control over the brand of your car or how difficult the installation will be, you can choose to minimize your alternator repair costs by using a remanufactured alternator and having a AutoNation Mobile Service technician do the work for you. 

The average cost of an alternator repair will normally range between approximately $400 and $1,000. This includes the cost of the new or remanufactured alternator, as well as the time needed to diagnose the charging system, remove the old alternator, install the new alternator, and test the system afterward. Your AutoNation Mobile Service technician can give you a more precise alternator repair quote, based on your car and the alternator cost for the new or remanufactured alternator you choose to use. 

What’s the Difference Between a New and a Remanufactured Alternator? 

A new alternator has never been used and should give you years of dependable service right out of the box (as long as it has been made by a reputable company). A remanufactured alternator has been used until it failed (or the car it was in was junked for parts) and has then had all of its internal parts replaced and reinstalled in the original case. Both new and remanufactured alternators should come with a warranty. For the average car, a remanufactured alternator should give you good service, especially if you are on a budget or don’t plan to keep your car for a very long time. The remanufactured alternator cost will also be lower than that of a new alternator.  

Stay Away From Used or Rebuilt Alternators 

What you should be sure to avoid are lower-priced used or rebuilt alternators. These either came out of a junked car (used) or have failed and had only the faulty parts replaced (rebuilt). The alternator cost of a used or rebuilt alternator will be significantly lower than that of a new or a remanufactured alternator. Neither of these types of alternators usually comes with a warranty, so you’re on your own if they fail. Keep in mind that you won’t just need to buy another used or rebuilt alternator if this happens – you’ll also be on the hook for the diagnosis and installation costs all over again. There go your savings! 

Voltage Regulator 

What Does a Voltage Regulator Do? 

The voltage regulator is the part of the charging system that regulates the voltage that is generated by the alternator. Because the alternator can produce a voltage that is higher than what the car’s charging and electrical system can safely handle, the voltage regulator is there to keep it within the proper range, typically between 13.5 and 14.5 volts. This is the voltage that will both power the car’s electrical system and recharge the battery without causing any problems.  

Depending on the vehicle, the voltage regulator can be located inside the alternator, outside of the alternator, or it can be built right into the engine control module (ECM) on newer vehicles. 

What Causes the Voltage Regulator to Fail? 

The voltage regulator is located under the hood and operates in a hostile environment. A voltage regulator can be subjected to heat, cold, leaking oil or coolant, impacts coming through the suspension from bad roads and potholes, rainwater and slush that gets kicked up from the road surface, and many other hazards. Wear and tear, high mileage, and physical damage to the voltage regulator circuitry and wiring can also be responsible for problems. There are many potential causes of a voltage regulator’s failure to maintain a correct and steady voltage level. Here are some symptoms that may be the result of a voltage regulator failure: 

What Does it Cost to Replace a Voltage Regulator? 

The cost of replacing your voltage regulator depends on several factors: 

Taking all these factors into account, replacing your voltage regulator could cost anywhere from less than $100 for a simple externally-located voltage regulator replaced by an independent mechanic, to well over $1,000 if the ECM needs replacement and a dealer does it. 

How Do You Test a Voltage Regulator? 

To test a voltage regulator, a digital multimeter is used. This is an electronic diagnostic instrument that measures electrical values such as voltage, current, and resistance. The process used to test a voltage regulator follows these steps: 

  1. With the car shut off, test the battery’s voltage, which should be approximately 12.5 volts 
  1. With the car idling in Neutral or Park, test the battery’s voltage, which should be at least 13.8 volts, but not more than 14.2 volts. This is enough to charge the battery, but not so much that it can damage the car’s electrical system. 
  1. Accelerate the idling vehicle to between 1500 and 2000 RPM and test the voltage. It should max out just under 14 volts and definitely stay below the 14.2 mark. If it goes past 15 volts, there is a problem with the voltage regulator sending too much voltage into the car’s electrical system and potentially causing damage – the voltage regulator needs to be replaced. 


What Does a Car Battery Do? 

Your car’s battery is the source of the energy needed to get your car started. When your engine is shut off, the battery also provides the power needed for the vehicle’s radio station presets, clock, security system, and computer memory. 

The car battery is made up of a plastic case that contains plates of lead and lead dioxide. These plates are covered with an electrolyte solution made of sulfuric acid and water. A chemical reaction between the plates and the electrolyte produces an electrical current that allows the battery to do its job. 

What Are the Causes of a Bad Car Battery?

 Just about all car batteries will eventually wear out and fail. This is most commonly because the materials inside it can no longer provide a strong enough chemical reaction to make sufficient car battery voltage to start the car. This process can be accelerated if you live in a very cold climate, where starting a cold engine requires more car battery voltage and the cold naturally reduces a car battery’s power output. It can also be sped up if you reside in a very hot place, due to the destructive effects of extreme heat on the materials that make up the battery. Other causes include battery cables that are loose or corroded, a low electrolyte level, draining the car battery’s charge by leaving your lights on overnight, and a charging system that isn’t working properly. 

What Are the Symptoms of a Bad Car Battery?

There are several ways to tell that your car battery is bad and about to fail. Please pay attention if you experience any of these, and have them checked out by a mechanic before they get any worse. Being stranded by the side of the road with a dead car battery is no fun! 

How Do You Fix a Bad Battery? 

The quick and easy solution to this is a car battery replacement! Before you do this, it is essential to determine whether the car battery is completely to blame. This is where a mechanic can help. The mechanic can: 

  1. Verify that your car battery is actually dead – it may be possible to recharge it 
  1. Check your charging system to make sure that it is recharging the car battery properly 
  1. Check that your starting system is working as it should 

The benefit of all this is to assure you that the car battery replacement if it is necessary, will solve the problem.  

What Causes the Charging System to Fail? 

The charging system in your car can fail for a variety of reasons, including: 

Because the system is so complex, your best bet is to have a mechanic troubleshoot your charging system and pinpoint the exact cause so that it can be fixed correctly the first time! 

What Should I Do If My Charging System Has A Problem? 

If you suspect you have a problem with your charging system, make an appointment with a mobile technician from AutoNation Mobile Service as soon as possible to have your vehicle inspected and repaired and to prevent further damage. But before you call to make an appointment, collect as much information as you can, including under what specific circumstances the problem occurs, to assist your technician in diagnosing the problem. The more details you can provide, the easier it will be for your mechanic to find the cause of the charging system problem.