Can A Bad Alternator Cause Transmission Problems?

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Modern cars make use of automatic transmission which is controlled by the car computer powered by the car battery.

Given that the car alternator is responsible for recharging the car battery, what will happen to the transmission when the alternator becomes bad or starts failing?

So, can a bad alternator cause transmission problems? Yes, a bad alternator can cause transmission problems or issues although not directly.

The alternator is an essential car component whose primary duty in the car is to ensure the car battery is recharged as soon as the power is used up. 

The car battery provides the voltage that runs many aspects of the car’s electrical system including the car computer.

Modern cars make use of computer systems that afford the driver minimal interference during driving. In automatic cars, this computers system is responsible for shifting the transmission gears amongst other things.

Therefore, when the automotive alternator is bad, the car battery is not charged adequately and therefore becomes low on voltage.

This causes the computer not to be able to officiate the shift in transmission gear properly leading to problems such as stalling, surges, and rough shifts.

In severe cases, an incorrect shift in the transmission gear may cause engine and transmission failure which will bring about other drive symptoms.

Effect of a bad alternator on transmission

While a bad alternator may not directly cause transmission problems, the resulting voltage issues from a bad alternator can bring about several problems that could become symptomatic.

Low voltage can mess with the car sensor systems such as the transmission range sensors. When this happens, the car may manifest symptoms such as dying in idle, limb mode that is being locked in a single gear, incorrect gear change amongst others.

When these symptoms begin to show up and the car owner ignores the warning signs and tries to drive the car irrespective, this could lead to a full-blown transmission failure.

The low voltage output from a bad alternator creates a problem with the transmission range sensors and causes a range of differing symptoms.

For some, the symptom will include the car dying at idle, the radio speakers acting up, the dome light not working. The array of malfunction in the car electric system does not follow any particular other and cannot be predicted.

Car owners experiencing similar manifestations with their car should get the car alternator tested using a multimeter and have it changed if determined that it is behind the transmission problem.

So, while a bad alternator may not directly cause any transmission problem, the voltage drops as a result of alternator failure do. This is especially true on modern vehicles whose transmission is electronically controlled and therefore depends on the alternator’s voltage output.

Modern cars made from around 1993 to date are configured in a way that their gear shift won’t correctly unless the amount of voltage is optimal.

Aside from low alternator voltage, whenever there is a high or spike in alternator voltage, this could potentially create damaging effects on some of the car devices and cause them to misbehave.

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How does a bad alternator cause transmission problems?

The modern car is a conglomeration of different operating systems with each interdependent on the proper working of the other. Whenever one of the systems fails, the related or connected system will consequently succumb to the failure as well.

All the systems in the modern car are somehow linked or connected with the central computer system and give it almost full control of the car.

Many aspects of the car’s performance are controlled by this computer system affording driverless control during a drive.

The alternator is central to the proper working condition of this computer and therefore affects a lot of things when bad including transmission in a modern car, the car radio system, the catalytic converter as well as the car tire pressure amongst other things.

The interdependent systems in today’s modern car include the engine management system, the drivetrain system, and the chassis management system.

These three systems are interdependent on one another and work synergistically to bring about the proper running of the car.

For example, shift point optimization, as well as fuel usage efficiency, is brought about by communication between the engine management system and the drivetrain system.

Also, car aspects such as traction, anti-lock brakes, stability control, and cruise are modulated by the communication between the engine management systems and the chassis management system.

From this, we can see that the engine is central to the proper functionality of the car. Whenever it develops any problem, these systems which are connected to the engine will have to make some adjustments in their parameters to accommodate or compensate for the problem with the engine to continue to maintain the car performance, emission compliance, fuel usage economy, and other aspects of the car.

An example of such a situation when the car engine performs suboptimally is when the alternator is bad and only gives out a low voltage outage output.

When this happens, it will slow down the engine revolution per minute through the transmission altering the engine programming. This is done to reduce the load on the car engine.

The outcome of a consistently low alternator voltage output depends on the programmed strategy. For some, the transmission is programmed in such a way that when the alternator voltage is low, the car engine is forced to maintain a lower gear.

Chances that the car stays in this lower gear are higher than the increase in the engine revolution or increase in alternator speed. 

So, generally, the low voltage output of a bad alternator will affect the gear shift system as some programming tend to keep the car engine in a lower gear during this time.

The second aspect of this problem is when the alternators have integrated voltage regulators. Such an alternator when they become bad may send a power surge throughout the system before failing.

This unwanted power can cause a catastrophic chain of events if not well controlled. The car computer system detects this surge and redirects it away from susceptible car components such as the powertrain control module.

Without power reaching the power train transmission module, transmission is bound to fail outrightly. If this does not happen, then the effect may be directed to the clutch pressure and shift points. In other instances, it is the converter lock-up and fluid controls that suffer the consequences as they are being deprived of transmission.

When the alternator is bad, another when it can cause transmission problems is via creating a host of engine symptoms which consequently cause transmission problems. Let’s look at a couple of examples of how a bad alternator can cause engine symptoms and how this can lead to transmission issues.

A bad alternator generates a lower current supply, this causes a cutdown in the amount of electric current sent to various car parts including the ignition system.

When the ignition system is deprived of electric current, it malfunctions in a way that causes it to eject unburned fuel through the exhaust and into the catalytic converter leading to a high converter temperature.

This will be misinterpreted by the engine computer which assumes the high converter temperature is due to increased load on the engine and will therefore cause a drop in transmission to reduce this load thereby creating a transmission problem.

How does a bad alternator cause transmission shifting problems?

Could a bad alternator be responsible for the harsh or rough shift experience sometimes when changing from one gear to the other? Yes, a bad alternator could be responsible for such a problem.

Modern cars have computers that control electronic transmission. They run on the voltage from the car battery.

If the alternators fail and the car battery voltage consequently drops below the optimal voltage required by the computer to work, the car may become locked in a single gear (limp mode) or experience a harsh or rough gear shift.

Other signs you may experience in your car to further confirm your shifting problem is due to a bad alternator include flickering or dimming of the car’s headlights, strange noises coming from under the car’s hood, usually, a whining or rattling noise, dead car battery, stalling or difficulty in starting the are engines, especially in the morning and malfunctioning of other electrical accessories in the car.

It is not every time any of these signs are noticed that it may signify a failing alternator. Sometimes, it could be a problem with the alternator belt, the alternator pulley, or other engine parts and not the alternator itself.

Before rushing to have the alternator replaced, the alternator can be tested for using an ammeter or multimeter which is capable of measuring both the voltage and current or amperage.

Can A Bad Alternator Cause Transmission Problems – Conclusion

Yes, a bad alternator can cause transmission problems. This is primarily as a result of the low voltage output of bad alternators which hampers the car computer and creates problems such as incorrect gear shift amongst others.

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