Changed Alternator Now Car Won’t Start – Reasons And Solutions

When doing with cars’ engines, you may find new issues, particularly if you replace parts.

Installing a broken component, incorrect installation steps, and various difficulties can all lead to your car not starting.

Have you ever experienced a changed alternator now car won’t start? It’s frustrating after you spend time replacing it, but it puts your car in a worse situation.

If you get stuck in this puzzle, this post is for you. Let’s keep reading to find the causes and solutions for the problem.

Why Have You Changed Alternator Now Car Won’t Start?

Changed Alternator Now Car Won't Start

It can be because some units in the replaced alternator are broken.

Moreover, other vehicle components will lead to this issue, such as a bad battery, unstable connections, damaged fuel pump, corrosion, failed ignition, etc.

If you change a new alternator but car won’t start, continue reading to find the precise root cause behind.

Dead/Weak Battery

A part closely related to the operation of a vehicle alternator is the battery.

When the automobile operates, the alternator supplies electricity to the battery, ensuring it does not lose charge. Thus, please always tighten the battery terminal carefully and properly.

A dead battery can happen due to various factors. The most prevalent is that the battery discharges completely even when you alternator has been replaced.

This could indicate that your alternator failed to charge the battery.

One solution is to charge the battery at an auto shop or to idle your car after a jumpstart.

Because you installed a new alternator, your vehicle might start right up after a jumpstart.

Remember that you should not turn off your car until you get to the charging station because the alternator might not fully charge the battery.

Loose/Bad Connections

You replaced alternator and battery car still won’t start? It might be a problem with battery cables or connections.

You will need to detach a few wires when changing a new alternator. Even if you are meticulous in reconnecting them, one or two may slip through the cracks.

Check each connection to ensure it is secure, then try reconnecting some of the cables you previously disconnected.

Sometimes it’s the little things that we often overlook. That is why, when reinstalling components, double-checking all wires is a good habit.


Corrosion not only prevents the battery from producing power, but it can also chew through wiring.

Corrosion prevention is vital because it can impair critical parts of your vehicle, putting everyone in the car in danger.

Your battery is one place where corrosion can occur, preventing your vehicle from starting.

A car battery contains acid and a post to which you connect wires to power your vehicle’s parts. The corrosion process begins when acid contacts the metal post.

Always remember to separate the cables when removing the corrosion from the battery to minimize shock.

Since you’ll need to use water in this process, when cleaning the battery, no cables should be attached to it.

Regular inspections might assist you in monitoring the state of the corrosion.

Bad Fuel Pump

A lack of fuel is also to blame for when the car won’t start after replacing alternator.

The fuel pump in an automobile is responsible for delivering power to the engine. If your car doesn’t start, there could be a few problems with your faulty fuel pump.

The most-seen issue is the fuel filter becomes blocked. A filter on your gasoline pump helps keep dirt out of the engine. When the filter becomes clogged, the pump will struggle to feed fuel to your engine.

Another possibility is that the fuel pump has failed. A faulty pump might be caused by old age or a high-usage vehicle. If this occurs, you should engage a mechanic to replace it.

When something breaks or stops working properly after replacing a new component, we usually look at the most recently installed item.

Thus, we often overlook the other sections that may not be immediately affected by the new installation but may still fail.

Faulty Unit

You may have changed your alternator, but there is still a risk that the new alternator is defective.

A malfunctioning unit has the potential to fail even when new. So, you must have a warranty to resolve any issue.

If the new alternator fails even though it is brand new, contact the car shop where you buy the service to change the component.

Car components have warranties, yet the duration for replacement varies based on the merchant or unit.

As a result, you should ask the merchant or mechanic whether you can repair the car component you purchased from them when it breaks within a certain time frame.

Faulty Spark Plug

If your spark plugs aren’t performing properly, you should replace them. Failing to get a spark from the spark plug can also prevent the automobile from starting.

Check to see whether your spark plug works well for your automobile; if not, change it. You may also need to replace the plug tips, which might affect the spark.

Defective Or Bad Ignition Switch/Coil

Once you change the alternator but your vehicle still cannot start, the problem might be with the ignition system, especially the coil and switch.

After a long time of use, there might be a broken or burnt wire in the ignition switch. This makes your car unable to start and drive.

Ask a mechanic to check the ignition coil and switch whenever you have trouble starting the vehicle. Replacing the failed part with a new one is the ideal solution to handle problems.

What Should I Do When I Changed The Alternator Car Won’t Start?

What Should I Do When I Changed The Alternator Car Won't Start?

Test The Alternator

Even brand-new components can fail at times because of a manufacturing defect. Test the new alternator with your handy multimeter to confirm it works properly.

You can do this step before you replace the old one with it. A bad alternator can negatively affect other components (such as a battery, etc.)

Test The Battery

The voltage in your car battery should be between 12.6 and 14.5 volts. This is because the battery cannot be jumped without being replaced or charged if it is too exhausted.

A weak/dead battery can make your car unable to start even if you change a new alternator.

Check The Connections

Have you double-checked that everything is in order? Check and retrace your actions to ensure you got everything during installation.

Check Other Electrical Components

Suppose the three checking ways above don’t show any problems; it’s time to check other engine components. They might include a starter, oil pump, fuel pump, transmission, etc.

In case you cannot find the issue yourself, you should look for a professional mechanic to check and diagnose your engine with better skills and tools.

How To Change The Alternator Correctly

How To Change The Alternator Correctly

Required Tools:

  • A new and good-quality  alternator 
  • Voltmeter
  • Belt tensioner
  • Hand tools
  • Rags
  • Gloves
  • Replacement serpentine belt

Step-By-Step Instructions:

  • Disconnect the car battery: First and foremost, unhook the engine battery.
    If you don’t unplug the battery, you’ll almost certainly ground a live wire throughout the operation. This causes a slew of unpleasant things, not the least of which is that you get shocked.
  • Unplug the wires: Disconnect the wires from the alternator’s back after disconnecting the battery in the above step.
    This is usually an easy process, but should you be unsure of identifying them, label them as you take them off.
  • Remove the belt: One stumbling block for alternator changing is removing the belt from the engine’s pulley.
    A tensioner pulley can be found somewhere in your car. You must move it sufficiently to let the belt slip off it.

Screw-type or rod-end tensioners are available on many car models and create tension by rotating a bolt through the threads to raise or reduce the rod length.

In this situation, simply crank the bolt/rod end with a socket or wrench until it has enough tension to allow you to take off the belt.

  • Remove the bolts: After you take off the belt, simply remove the bolts that link the alternator to the engine bracket, and you’re ready to go.
    At least three bolts had to be removed: one in the front and the others in the back.
  • Check the replacement item: You’re almost there with the old/failed alternator in your hand.

As you know where everything is, installing the new one back in should be considerably faster. Before reassembly, inspect the replacement item to ensure it will function properly.

  • Install the new one: Simply reverse the removal stages, giving special attention to tensioning and belt routing.
    If you don’t get familiar with installing a car component, you can write down the removal steps to ensure you install them properly later.


Why Is My New Alternator Not Charging My Battery?

Your new alternator not charging the battery stems from many reasons. Mostly, it is not the issue of the alternator, but other components of the car engine have troubles:

  • Corrosion of the battery terminal: The alternator cannot charge the battery due to corrosion. The foam or chemical corrodes the terminals and prevents them from conducting power.
  • Oil spillage: This also might affect your alternator’s operation. When you fill up the oil, it may spill into your alternator. The oil then sticks, gathering a lot of dust and clogging the alternator.
  • A blown alternator fuse: An alternator fuse might blow while starting the automobile or driving.
    An excessive power spike causes it. No current will travel to the battery to operate the car if this occurs.
  • A bad starter: It occurs when your cables are mismatched, and there is a potential that the occurrence will burn out your alternator. It can also cause your car’s accessories to catch fire.
  • A bad jumpstart comes when you mismatch your cables. So, the event will likely burn your alternator. It can also fry your car’s accessories.
  • A pulley and belt: An alternator that lacks a pulley and belt will not function.
    The serpentine belt might fail due to a crack or simply being old. Your car’s accessories will not work properly when the belt is not in good condition.

How Many Hours Of Labor Is Alternator Replacement?

An alternator replacement typically takes 2 to 3 hours. That’s roughly $200 in labor expenditures, depending on the hourly rate of each mechanic.

A new alternator will cost about $200 – $350 if you utilize OEM parts. In case you don’t mind buying aftermarket parts, a new part might cost between $100 and $200.

What Is The Life Expectancy Of A Car Alternator?

Most alternators have a lifespan from 80,000 to 150,000 miles. An alternator typically lasts 7 years.


The case: changed alternator now car won’t start is quite common. So you don’t need to worry too much about this. The article also mentioned some ways to check when encountering a problem.

Besides, during the alternator replacement process, you should be meticulous and check it many times to ensure there are no problems during the installation steps.

If you are struggling with other damaged parts, take them to a mechanic shop for faster diagnosis and solution. At the same time, this will ensure your safety while driving.

If you have any questions, don’t hesitate to ask us by leaving a comment below. Have a safe ride!

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