Bad Alternators: Symptoms, Replacement & Repair Costs

Blog/ Bad Alternators: Symptoms, Replacement & Repair Costs


AuthorSarah RobinsonCategory General Automotive

Let’s say you turned the ignition key of your car and instead of the engine getting fired up…you hear fast, strange clicks. What comes to mind?

You’d likely assume that your car battery is bad and needs a change.

You might be right but if it’s something as serious as a bad alternator…then that’s an expensive assumption. Why?

Well, if your car has a bad alternator, changing the battery will still leave you with the same problem and in the end…a dead battery.

A dead battery equals a dead car. In this article, you’ll find out all there is to know about alternators and save yourself from making a costly assumption.

Let’s begin…

What Is An Alternator?

Your car gets the charge it needs – to power up the engine – from the battery. Although some car batteries have huge storage capacities, there’s still a need for a built-in battery charger.

This is where the alternator comes in.

The alternator charges the battery while your car is running by turning its mechanical energy into electrical energy. Hence, it provides an abundant supply of electrical power to the engine, headlights, stereo, etc.

The alternator is driven by the serpentine belt [also called the drive belt] and you’ll find it attached to your car engine.

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How Does An Alternator Work?

We’ve established that an alternator’s main job is to sustain the car battery by keeping it charged. It does this by using power from the engine and sending it to the battery to charge it. The alternator receives electrical power, from the engine, through the serpentine belt [drive belt]. Now you can see how important the serpentine belt is.

That’s why it’s essential to always make sure this belt remains tight and replaced when necessary. An alternator’s output is direct current [DC]. Once the pulley is rotated, alternating current [AC] will pass through a magnetic field and generate electrical current. The electrical current is then converted to direct current through the rectifier. You can refer to the alternator as a generator if you like…you’ll still be on the right path as it works like one.

What Causes An Alternator To Go Bad?

Why might an alternator go bad? Here are the reasons:

  • Weak Diodes: An alternator consists of three smaller alternators. These smaller alternators provide different levels of electrical power. These electrical power levels also have their pair of diodes. Once a pair of diodes fail, the rest will have to keep up and bear a larger share of the current capacity. Your car will still run unless all three pairs of diodes fail. When this happens, your car will be unable to carry out its electrical functions.
  • Inadequate Field Voltage: An alternator is required to have a field voltage of about 12 – 15 volts to be able to produce electrical power. Anything lesser than this will undermine the alternator’s performance. You can always make use of a voltmeter to check if enough volts are being transmitted to your car’s alternator.
  • Faulty Bearings: There are high-precision needle bearings that the alternator rotates on. These bearings are noiseless so you won’t hear them normally. When these bearings become faulty, the alternator will make a deep, loud noise. This usually sounds like two or more metals rubbing against each other. In the case of a faulty bearing, it’s best to have the alternator replaced.
  • Worn-out Rotation Belt: The alternator makes use of a rotation belt to generate electrical power. Over time, this rotation belt becomes loose and could slip as it wears out. The rotation belt is located close to the alternator’s pulley. If the belt looks cracked or shiny then you need to have your alternator replaced.

What Are The Warning Signs Of A Bad Alternator?

It’s possible to miss the warning signs of a failing alternator. This is because your car’s battery will still keep your engine running from its stored-up charge [gotten from the alternator before it went bad]. Once the battery has used up this stored-up charge, then your car will stop working. However, here are a few warning signs that you’ve got a bad alternator:

  • Dead Battery: If you replaced your dead battery with a new one and it dies again then it’s a sign that the problem is from your alternator and not your car battery. A brand-new battery and a bad alternator will always leave you stranded…with a dead car.
  • Engine Stalls: If your car engine stops all of a sudden while you’re driving, it’s likely an alternator problem. Without an adequate supply of electrical power – provided by the alternator – your engine will stall.
  • Dimming Headlights: A bad alternator causes voltage variations and will make your car’s headlights dim or to flicker. You’d usually notice this problem early if you observe closely. If you notice that your car’s headlights dim when the engine is idle and becomes brighter when you fire it up then it means your alternator is undercharged and will soon die out. In some cars, an undercharging alternator will highlight a ‘check engine light’ notification on the dashboard.
  • Bad Smell: Noticed a smell similar to that of ‘burning plastic’? It means the alternator wires or internals are burnt. If it smells acidic instead, it’s a sign that the alternator is overcharging which can result in a leaky, damaged battery.

How Much Does An Alternator Cost?

Once you’ve discovered that your car’s alternator has gone bad, the next step would be to remove it and have it replaced. Now you ask, “What’s the cost to replace an alternator?” Well, alternator costs can range from $300 to about $1,000 for parts and labor. The cost to replace an alternator also depends on your car’s model, brand and production date.

If your car is an old model, you will find the alternator easier to work on and the cost of replacement…cheaper.

For newer car models, the alternator costs are more on the high side. Why? It’s because newer car models mostly need special tools and expertise to work on the alternators.

However, if you want to save up on labor costs, you can have the alternator replaced yourself by using standard tools.

Should I Buy a Used, Rebuilt or Refurbished Alternator?

You’re probably wondering if you can save money with a used, rebuilt or refurbished alternator option. Well, let’s first clear the air on the difference between these three. Replacing your car alternator with a used one is the cheapest option but we won’t recommend this. This is because used alternators usually won’t come with a warranty and can go bad at any time…bringing you back to square zero where you started.

A rebuilt alternator is one that has once failed but only had the failed parts replaced. The remaining parts will still be the same…leaving room for future problems. In the case of refurbished alternators, they’re a better choice. They usually come with a warranty [1 year] and have had both the failed and working internals replaced with a new casing.

So, if you’re looking to save money, a refurbished alternator is a better option over a new alternator and the best option over rebuilt or used alternators.

Can I Replace My Alternator Myself?

Sure, you can. Although you’d need a bit of technical know-how to make the replacement successful. If you’ve decided to have your alternator replaced yourself, you can use these tips:

  • First, disconnect the battery from the alternator.
  • Next, disconnect the wires behind the alternator [you can label them to know where to fix them back].
  • Using a wrench, remove the rotation belt from the pulley.
  • Once you’ve got the belt out of the way, remove all the bolts attaching the alternator to the bracket.
  • Fetch the new alternator.
  • Observe the new alternator and check if it’s the same with the old one that was removed. Here, you’re carefully checking that the belt, bolts, pulley size and everything else are the same as the old one.
  • Once you’ve confirmed that, you can then re-install the alternator in reverse order of the removal.

Is An Alternator Replacement Worth It?

So, you decided to replace your car’s alternator and when you got to the mechanic, you’re given another news: Your serpentine belt [drive belt], tensioner, battery, and idle roller also needs changing. Now your next question would be if it’s worth it. Of course…it is.

Your car mechanic is just looking out for you. Drive belts, tensioners, batteries, and idler rollers won’t often last as long as your car. If you’re bothered about the additional labor costs for these new parts, they usually won’t cost up to $100 [although this depends on your car model] and would be part of the alternator removal cost. When removing your alternator, the serpentine belt, aka drive belt, is first removed.

If you haven’t replaced the belt before or over some time, your mechanic will advise you to have it replaced with a new one, Sometimes, though rare, the wiring harness plug for your alternator will also need replacing. This will only be necessary when the plug has melted due to excessive heat. Before your mechanic removes the alternator, he’d carry out a quick test on the battery.

This will let him know if the battery needs changing or not. When your alternator goes bad, your car still looks for power to function before it stops working. This power strain will be put on the car battery until it drains and in most cases, the battery cells get damaged too. If you’re lucky and the battery survives this strain then you don’t need to have it changed.

So, if you’re still interested in keeping your car…listening to your mechanic and replacing all these parts will save you money and stress in the long run.

What Are Your Options If You Don’t Want To Replace The Alternator?

If you’ve weighed the alternator replacement costs and it’s too high for you [because of your car model] or you feel it’s not worth it then you can try any of these options:

Repair Your Car’s Alternator.

Having an alternator repair done simply means getting the malfunctioning parts fixed. This will cost less than replacing it with a new one depending on the parts that need changing. Of course…this is a temporary solution to your car’s alternator problem as you can’t rest assured that new problems won’t spring up soon.

The price for an alternator repair cost would depend on the other parts that have been damaged. It may be just a problem with the alternator’s belt or the whole alternator is damaged. On average, an alternator repair cost would likely range between $450 - $600.

Sell Your Car As It Is.

When your alternator goes bad, you can’t drive your car anywhere…even for repairs. To move your car out, you’d need to have it towed. In the end, you’re looking at the cost of towing your car, labor costs and cost for parts. Getting your alternator repaired or replaced is a decision you’d need to make sooner or later as long as you drive a car. Your safety and that of your passenger(s) will depend greatly on it. So, if the alternator costs are a no-go for you [both for replacement and repair] or the mechanical problems just keep piling up, then selling your car in its state will be a better option for you.

This is where SellMax comes in, we’ll give you a quote for your car and if you like it…you take it. If you’ve been asking how can “How can I sell my car” this is your answer. No stress on your part as we’d take it up from there. We’ll come to you and tow your car for free and that’s not all…we leave you with cash in place of your car.

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