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Can Bad Alternator Cause Transmission Problems?


Alternator plays a crucial role in the car by charging the battery to supply the car with sufficient power. But just how important is the alternator and can bad alternator cause transmission problems?

A faulty alternator can cause transmission problems alongside other problems. When the alternator is incapable of charging the battery and the battery runs down, the transmission system can shut down.

This article explains what you need to know about alternators and transmission, the symptoms of a faulty alternative, and how to fix a bad alternator.

Can A Bad Alternator Cause Transmission Problems?

If a car alternator is bad and the car battery gets run down, the computer system won’t be able to shift the transmission gears properly. The transmission and engine can go into failure mode resulting in other drive symptoms.


Alternatively, a low battery voltage can force the transmission into safe mode that will put the transmission in third gear. Transmission problems manifest in the form of poor acceleration, hesitation, and stalling.

Symptoms Of A Failing Alternator

The alternator is an essential part of the car’s electrical system that turns the energy from the crankshaft into electricity to power the car’s computer system. When the alternator begins to fail, it can result in multiple problems that can cause the car to break down.

These are the symptoms that indicate a faulty alternator.

The Indicator Light

Cars come with an indicator light on the dashboard that switches on when there’s something wrong with the computer system. When this light is on, it might be an indication that something is wrong with the alternator and your car is due for a check-up.

Flickering Headlights

The alternator supplies the headlights with power so when the headlights dim or flicker, it suggests a faulty alternator.

Electrical Failures

There are different parts of the car powered by the alternator. When the alternator gets faulty these components of the electrical system can experience failures. A failure in the radio, air conditioning, dashboard lights, and other parts of the electric system is a sign of a faulty alternator.

Strange Noises

Strange noises in the car can be due to different reasons. However, a faulty alternator can cause an unusual rattling in the engine. If this noise is accompanied by other signs of a failing alternator, you might want to check it out.

Difficult Starting The Car

A faulty alternator will result in an insufficient power supply to ignite the plug that kick-starts the engine. When you have trouble starting your car or the car suddenly stalls while running, it can be an indication of a failing alternator.

man can't start the car and angry for that

Battery Keeps Running Down

The alternator is responsible for charging the battery while the engine is running. If the engine suddenly shuts down and the battery is constantly drained, It’s a sign of a bad alternator.

Factors That Affects The Alternator

The factors that can affect the functionality of an alternator include the following.

A Bad Alternator

Alternators don’t last forever and their life span can last from 5 to 8 years. When the alternator has outlived its lifespan, it can begin to reduce in strength. An old alternator will result in electrical issues due to wear-outs. In this situation, you need to replace the alternator.

Computer Problem

Modern cars have a computer system that is the central control system for every component of the car including the alternator. If there’s a problem with the computer system, it will invariably affect the alternator’s functionality.

A car computer system failure will also affect other parts of the car. This way, it becomes easier to identify the car’s computer system has the problem.

Wiring Problems

Wires run through the car connecting one component to another. When one important wire within the electrical system is damaged, it can affect the alternator.

If the alternator isn’t charging the battery and the problem doesn’t seem to be from the computer system failure, it might be the wire.

Bad Fuse

Cars have fuses that make the alternator work. When this fuse blows out due to a power surge or damage due to old age, it can affect the alternator.

A bad fuse affects the capacity of the alternator to charge the battery. You can check the car manual for the location of the alternator fuse to check if it’s damaged.

Broken Belt

The alternator transforms the mechanical power generated by the belt and pulley into electrical energy for the car. When the alternator belt and pulleys are faulty, it will affect the alternator’s functionality.

How to Fix A Faulty Alternator

If your alternator is bad it will affect the transmission of energy from the battery to other parts of the car. Fixing an alternator can be a technical task. However, if you want to fix it yourself, you can follow these steps.


Purchase The Right Kit For Your Alternator

You need to identify the type of alternator you use and buy a regulator replacement kit. You also need a set of screwdrivers and brushes.

Disconnect The Car Battery

You should begin by disconnecting the battery to cut off the power supply. This is to avoid sparking a possible electric shock. You should begin by removing the black terminal followed by the red terminal.

Remove The Alternator

After disconnecting the battery, you can proceed to remove the alternator. First, take some pictures of the alternator to analyze the wire connection. You can then unclip the wire harness on the rear before unbolting the alternator.

The alternator in most cars is held down by a long bolt and a short bolt. The long bolt is at the alternator’s underside while the short bolt is at a bracket at the top of the alternator. The longer bolt requires a little effort to unbolt but it’s nothing you can’t do with a little patience and the right tools.

After removing the alternator, you can then proceed to remove the rear cover from the alternator.

Remove Old Regulator And Brushes and Replace Them

After removing the alternator, you can remove the regulator and brushes. First, try to take a picture of the regulator and brush before removing it. This might make reassembling it easier.

You can then proceed to install the new regulator and brushes. After which you can reconnect the wires and tighten the bolts. However, you should avoid over-tightening the bolt.

Refit The Rear Plastic Cover

After installing the new regulator and brushes you can then proceed to refit the rear plastic cover.

Refit The Alternator

You’re almost at the finish line and the last step is to refit the alternator. You should ensure the fan belt is tight or the alternator won’t function properly.

After following these steps, you can take the car for a ride. If everything is right, the alternator should charge the battery and the power transmission should return to normal.


A bad alternator can lead to transmission problems in different parts of the car. The best way to solve this problem is to identify the fault with the alternator and fix it.

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