Will A Bad Alternator Cause Rough Idle?

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A bad alternator will crumble the car’s electrical system and lead to several consequences. Unlike older vintage cars, modern cars are designed with increased dependency on electricity and cannot function properly without an adequate supply of it. In such a car, what will happen if the alternator goes bad?

So, will a bad alternator cause rough idle? Yes, a bad alternator will cause rough idle. The electrical demand for modern cars is considerably high as a good number of parts of the car runs on electricity.

In a modern vehicle, the car’s engine, fuel system, ignition system as well as emission system all depend on a specified voltage supply to run properly. Without this, the system malfunctions or slow down and create various types of problems in the car.

The car alternator is responsible for generating the voltage that keeps all of these systems running properly. Therefore, when the alternator goes bad, the voltage output reaching these systems is reduced and will cause them to malfunction, resulting in poor engine performance.

The effects of poor engine performance, therefore, include rough idle, stalling, poor acceleration, misfiring, hesitation amongst others. a bad alternator can therefore lead to a rough idle by causing a low voltage which brings about poor engine performance.

Aside from a bad alternator causing rough idle, one other car defect which could also cause rough idle is the failure of the water pump.

Whenever the water pump becomes bad, it causes the generation of a characteristic noise which is picked up by the knock sensor. the sensor’s interference in transmission and timing causes a rough idle.

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What are the signs of a bad alternator?

When talking about the car’s electric system, the alternator is most likely one of the most important components of this system and its failure could lead to grave consequences for other components of the system. 

Before a total or complete failure of the car alternator, certain signs or manifestations could be considered warning signs indicating an impending alternator failure.

The ability of the car owner or driver to recognize these signs at their early onset will help save with prompt replacement of the alternator and save other electrical accessories from getting damaged.

Without understanding the possible manifestations of a bad alternator, some car owners cause themselves unnecessary expenses, changing engine parts that have nothing to do with the problem while forgetting what the true culprit is.

When the car is idling rough for example, one may be confused about the cause of such a problem. This may lead to suspecting the ignition system and replacing its coils and plugs without seeing any result. There is, therefore, a need to know about some of these signs to prevent unnecessary spending.

So, let us take a look at some of the signs that signify a failing alternator.

  • Rough running
  • Dimming headlights
  • Malfunctioning or slow electronic accessories in the car
  • Dead car battery
  • Noise- usually growling or whining
  • Burning rubber smell
  • Battery warning light
  • Trouble starting 
  • Frequent stalling

Rough running

This depends on how much the car engine depends on electricity. Older diesel engine which does not use spark plugs has less need for electrical current. The car engine can drive the fuel pump and bring about combustion without needing the spark plugs.

Modern cars are however computerized and require a great deal of electricity. The required voltage needed to keep the car engine performing optimally is gotten from that which is provided by the alternator.

In such a car, a bad alternator will cause the engine computer, ignition system, fuel system as well as emission systems which depend highly on this voltage to fail and begin to malfunction leading to poor performance of the car engine. This explains the rough idle seen in a car with a bad alternator.

So, when experiencing rough idle with your car, be quick to check the alternator to ensure it is in good working condition. If found wanting, the alternator should be changed immediately to avoid causing further damage. Other manifestations that may be seen along with the rough idle include misfiring, stalling, hesitation, and poor acceleration.

Once the car alternator is bad, expect to begin to experience a bunch of problems, some are linked to the alternator function while others may not. The bad alternator will stop the car from moving, and from starting as well as prevent the battery from charging.

Not everyone knows about a bad alternator causing rough idle. Often experiencing rough idle, other systems in the car become the prime suspect, leading to a total waste of money and time. 

Dimming or flickering headlights

It is no surprise that one of the first signs noticed in a car with a bad alternator is dimming or flickering headlights. This is because the headlights are perhaps the greatest current users aside from the ignition system used to start the car.

When a car alternator is bad, the headlights should not be turned on except when necessary. This is because the headlights consume a considerable amount of charge and will cause the battery to run down more quickly.

However, when the headlights are turned on at night, the driver will soon notice the light shine dimmer than usual or intermittently flickers. Aside from the headlights, other lights on the car’s dashboard may also flicker when the car alternator goes bad.

These lights flicker because the bad alternator is unable to maintain them at a steady brightness. When the alternator is in good working condition, the headlights will keep a uniform shine and will not fluctuate with the speed of the car engine.

However, with a bad alternator, the headlights will be seen to increase in brightness when the car’s engine speed increases and vice versa. 

Slowed or malfunctioning electronic accessories

One of the signs of a bad alternator is that almost all the devices and gadgets in the car that makes use of electricity will begin to malfunction. This usually does not follow any particular order.

The car contains devices such as the clock, radio, air conditioner, power seats, and others that make use of electricity and are therefore adversely affected by the low current output of a bad alternator.

The car window, as well as doors, are electrically operated. When the alternator is bad, the window will whine up and down slower than usual. It may take all day to get the window back up and may require you to support it with your hands to get it all up.

Similarly, the doors lock system may become slow in responding to commands. The power seats, tape players, and others will become increasingly slow in their various functions.

A bad alternator cannot handle an increased load situation. For example, when the car windows are rolled down or up at the same time, the voltmeter connected to the car battery can be seen to indicate a considerable dip in the voltage output.

During this time, the increased load can lead to the dimming of the lights including the indoor lights, and could almost put off the car.

These same symptoms are noticed when the fan is put on or when additional electronic accessories are turned on.

The alternator gets so weak at some point it becomes unable to get the car started. Rather than guessing what could be wrong with the car, test the working state of the alternator by connecting a voltmeter or a multimeter across the terminals of the car battery while the alternator is in the car.

A reading of 12 volts should be expected in this instance. When the car engine is turned on, this reading should ideally increase by about 2 to 3 volts.

Dead battery

The car engine requires a charged battery to get started. Once the car has been turned on, the battery loses some of its charges in the process. while the engine is running, the alternator generates the current which is used to recharge the car battery and keeps it fully charged.

However, when the alternator goes bad, this does not happen, that is, the alternator will not recharge the car battery. This will cause the car battery to become completely discharged.

A dead or flat battery will be unable to get the car started. Therefore, if you are always experiencing a battery rundown, especially when the car is parked overnight, you may have a bad alternator in your car which is unable to charge the car battery.

Whining or growling noise

Have you ever noticed a growling or whining or grinding noise coming from under the car’s hood? One of the common causes of such noise is a bad alternator.

The part of the alternator that causes such noise is the alternator bearing, which is the moving part of the alternator. When the alternator bearing fails, the alternator belt and eventually the entire alternator becomes bad.

Will A Bad Alternator Cause Rough Idle – Conclusion

Idling rough is one of the possible outcomes of a bad alternator. A bad alternator causes a reduced voltage output which reduces the engine performance resulting in rough idle, stalling, poor acceleration, and a host of other engine symptoms.

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