What Does An Alternator Warning Light Mean? [ANSWERED]

Getting any light on the dash can be pretty alarming, but the alternator warning light is a sure sign things aren’t right with your alternator or the battery.

Below we will highlight what an illuminated alternator warning lamp could mean and other symptoms that may help you diagnose the problem.

Usually, this warning light goes off within 2 seconds of starting your car, but if it stays on for longer than this or comes on when you’re driving, you have a problem.

Is an Alternator Warning Light (Battery Warning Lamp) Dangerous?

If the alternator light turns off within 2 or 3 seconds, you can be sure that your battery and alternator are working just fine.
If the alternator warning light remains on for longer when you start the car, you have a problem with the battery or the alternator.
When the light stays on, the ECU has detected an issue with the charging system.

If the light comes on when you are driving the car, this indicates an alternator problem and that the alternator is not charging the battery sufficiently.

What to do when the alternator warning light comes on and stays on

As mentioned, the problem could be your alternator or the battery. The best thing to do if this light comes on when you’re driving is to get to a place of safety off the highway as soon as possible.

Depending on how bad the alternator isn’t able to charge the battery or how bad the battery cannot accept the alternator’s charge dictates how long you can drive before the car shuts off.
To prolong the time, you can drive the car with the alternator warning lamp on and turn off all electrical components, including stereo heated screens, electric seats, and heated seats, electric wing mirrors.

All these modern conveniences will drain the battery very quickly. Also, air conditioning will use up an awful lot of charge too.

You need to test the alternator and the battery as soon as possible, and you can do this with a multimeter. The battery at a standstill should read 12.6 volts. There are other tests you can do on the battery and the alternator, and I have included a handy video for you to watch below.

https://youtu.be/LGB6ZEjGm7Q

If in any doubt, you should go to a qualified technician to check the alternator and the battery. Normally the problem will be with one or the other. Still, if the battery has been continually draining much below 12V, it could be that it can never be fully recharged again, and you may have to replace this and the alternator.

Can I Drive With The Alternator Warning Lamp On?

Your car is still safe to drive with this warning light on. It won’t blow up or catch fire, but eventually, it will stop running.

 Therefore you must get off a fast-moving road and onto a quieter street where you can pull over when the car stops.

Even better would be to limp your car to a technician and ask him to check over the battery and the alternator.

When this light is illuminated, your car is still somewhat safe to drive, as you will have enough battery power to run the engine.

Sometimes the alternator warning lamp indicates a problem with a connection between the alternator and the battery. This could be due to corrosion on the connectors or loose cables. If this is the case, it’s a very cheap fix.

Signs of a Bad Alternator

Dim or Overly Bright Lights

A telltale sign that your alternator is going bad is if the lights dim and then get brighter when you push on the accelerator. If they sporadically get very bright and you blow bulbs, it could be a sign that the voltage regulator in the alternator is bad and is not controlling the current flow to all your car’s other electrical systems.

This can be expensive because too much charge or voltage can ruin the battery and other delicate electrical circuits.

Dead Battery

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If you’ve recently replaced the battery only for it to be weak again, this is a sign that your alternator is killing your battery. This could be because it overcharges the battery or drains current away from the battery when the car is off.

If the battery is being overcharged, you may see the terminals smoking, and you may also see its case swelling.

If the battery is always low on charge in the morning, it could be that the alternator is drawing charge away from the battery. This will be caused by a bad alternator diode which allows the alternator to suck current away from the battery overnight.

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The problem with this is if the battery is continually drained below 12 V, it can become unsalvagable, and a new battery will be needed.

Slow or Malfunctioning Accessories

Because the alternator powers electrical components, when the car runs with a weak, damaged, or failing one, it will not run these components successfully. 

You may notice that your air-con or car fan doesn’t run as well as it should or that your car stereo is intermittent, and sometimes the volume is lower than you would want it to be.  

Your heated windshield may not clear as well as it should, and the windscreen wipers don’t appear to clear the rain as quickly as normal. All these point to the alternator’s inability to perform all the jobs you need.

Trouble Starting The Car or Frequent Stalling Out

If you have trouble starting your car and the alternator light is on, this indicates that either your battery or your alternator is defective. 

If your car stalls and stops and won’t restart, this is a sign that the alternator is not charging the battery and not providing the power needed when your car is running. 

It’s important to remember that the battery only powers the starting of your vehicle. When the engine is running, the serpentine belt turns the alternator which then recharges and provides all the powerful other electrical components when the car is running.

Alternator Growling or Whining Noises 

The alternator sits to the side of the engine and has bearings and rotating shafts inside. When bearings start going bad, as in a wheel bearing, you can hear a growling or grinding noise. This is the same for alternator bearings. 

The alternator pulley allows the engine to spin the alternator via the serpentine belt, which connects to the engine camshaft. The pulley bearings and rotor shaft spin millions of times a year and are subject to wear and tear. They are metal; they can cause whining and growling as they rub together as they become worn.

Burning Rubber Smell of Electrical Wires

If you smell burning, it’s more likely caused by the serpentine belt rather than anything inside the alternator itself. This is good because the serpentine belt is a cheap fix, whereas an alternator can run into hundreds of dollars for a new one.

 If you are confident you smell electrical burning, this indicates issues within the alternator, causing it to overheat. This could be down to the voltage regulator or that the alternator isn’t being cooled. This is more common in the winter, as sludge can clog up the air vents.

Bad Serpentine Belt

Years ago, cars had v-belts which were used to power different electrical systems from the engine. Nowadays, in most cars, one serpentine belt snakes through the car and powers water pumps, air conditioning, and the alternator, amongst others.

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This belt has to be kept taut because if it is slack, it cannot run through the engine bay correctly, and electrical components can start failing.  

This can be especially bad news if the water pump isn’t powered correctly. The water pump is needed to pump hot water away from the engine to the radiator. If your car is overheating and you hear a slapping noise, and your belt appears to be slack, this indicates that your serpentine belt needs to be tightened or replaced. 

Hard Steering

The serpentine belt and the alternator power the power steering pump. This pump compressors hydraulic fluid and enables the car steering wheel to turn far easier than it would do without this. 

Therefore, if you have recently found your car more difficult to turn, this indicates either a power steering pump issue on a serpentine belt or the alternator is starting to go bad.