I like auto zone and other places that sell parts and run scan tools on your vehicle, but lately I have been having customers come in saying that their battery or alternator needs to be replaced because these places have said so. A common misconception is just because they run a scan tool and give you a code for what is going on with your car doesn’t necessarily mean it’s because of that component. So, let’s look at some common signs and symptoms of a bad alternator:
Dead Battery:
There are other factors that can come into play to kill a battery. Of course, they do eventually weaken and die but if your alternator goes bad, the battery will have to take on the responsibility of keeping the car running and eventually it will give out. The battery is in charge of getting power to the starter, once the engine starts the alternator takes over and supplies power to most of the systems in the car. The alternator is also responsible for recharging the battery. So, if your car won’t start and you have a dead battery, it’s always good to test the alternator as well. Normally, if the battery was drained due to a bad alternator you can charge the battery back to good use. When the battery is back to being fully charged you can hook up a multimeter (like this one: AstroAI digital Multimeter) and set it to DC volts and hook up the negative and positive leads to the battery terminals. If the battery is readying above 12 volts (a good battery should be around 12.4-12.6 volts) while the car is off, when you start the car the voltage should go up to between 13.9-14.8. If the voltage is reading any less than that, you know you have a problem with the alternator and cables to the alternator.
Check Engine Light or Charging Light:
If your alternator dies and doesn’t want to charge the battery anymore, you will most likely get a charging light such as a red battery light or even a check engine light with a code. For example, P0562 will pop when the ECM/PCM determines there is an irregular drop in voltage. This is a very common code that can pop up when your alternator goes bad.
Dim / flickering / Over Bright Headlights:
This one is tricky because there are several other options that can come into play such as flickering lights could be due to a bad ground wire. Basically, if your alternator is failing it won’t be able to supply the correct voltage needed to maintain the headlights bright. On the other hand, if your alternator is failing it can cause your headlights to flicker or even be overly bright.
Alternator Belt / Serpentine Belt:
This is really more related to the belt than the alternator itself but belts tend to stretch and crack overtime and when they stretch too much they won’t have the tension needed to properly turn the pulley to the alternator making the alternator less effective. It’s always good to check the belts for cracks and being loose.
Grinding or Growling Noises:
Sometimes it is hard to diagnose where a noise is coming from but if you hear this distinct noise coming from the alternator, you will definitely be able to tell that is where it is coming from. The alternator has a lot of components in it and when they start failing, you will definitely start hearing the noises it is making.
Conclusion:
Whenever your car won’t start, don’t always assume it is the battery or the starter. I’m going to make an article in the future on how you can further check and diagnose a bad starter. Thank you for reading and if you have any questions you can email me on the contact page.
