One of the most frustrating things you can have go wrong on a vehicle is a bad alternator. Without a functional alternator (doing its job properly), your car’s starter battery is going to lack proper charge and ultimately, you’ll be stranded.
The good thing is that an alternator doesn’t just go bad: it gives some signs first; signs that if you’re attentive, you will certainly ‘pick up’.
In the rare event that you’re not paying attention and the alternator already needs to be replaced, the seven (7) signs below will positively isolate it as the culprit, saving you from the stress of trial and error.
Let’s dig right into it. But, first, what does an alternator do? And why is it so central to an ICE?
Article Outline
What Does an Alternator Do?
An alternator is a copper, steel, iron, or aluminum affair that constitutes a magnetic field inside a stationary wire where the spinning magnets within the rotating magnetic field induce an alternating current (AC) which is ultimately converted to direct current (DC) by a rectifier.
The job of an alternator, in simple terms, is to provide direct current to run a vehicle’s electronics and while at it, charge the vehicle’s starter battery.
However, like all wear and tear items on a vehicle, the alternator eventually serves its course and needs a replacement.
When that time comes, here are seven (7) signs that will positively inform you that your alternator’s time is up.
7 Signs of a Bad Alternator
These signs are positive signs of a bad alternator. If you’re experiencing any of these, great chances are that you’re dealing with a bad alternator.
When you have two (2) or three (3) of these ‘symptoms’ present, you’re dealing with a confirmed case.
However, to positively isolate an alternator that has gone bad, consider checking out this article that details how to test an alternator without a multimeter.
1. Flat Battery
A flat starter battery is the first sign of an alternator that has gone bad. If you recently bought a starter battery and for unexplainable reasons, the battery goes flat, the alternator is likely not doing its job.
You see, the alternator has the sole mandate to charge the starter battery (in addition to providing power to the vehicle’s systems).
If, for any reason, the alternator fails in this duty, the battery steps in – and tries to hold forte, assuming things will return to normal sooner than later.
However, if they don’t, the battery literally gives itself out, so that your vehicle will keep on and in most cases, take you to your destination.
The challenge, usually, is that after you reach your destination, the battery is flat – and can’t start the car again.
If this ever happens to you, the alternator should be the first suspect.
2. Warning Light on the Cluster
The little red battery light that occasionally illuminates the cluster primarily serves to indicate that something is wrong with the starter battery.
However, that isn’t all the little red battery sign indicates.
If for any reason the alternator of your vehicle isn’t working as it should, you’ll also get this ‘notification’.
When/if it comes on – and you have zero reasons to suspect your starter battery – the alternator is likely the culprit (and it should be treated as such).
3. Random Electrical Failures
Ever attempted to use the sunroof of your vehicle and instead of it opening and closing automatically, it begins to work manually, powering off immediately when you take your finger off the switch?
Or, have you ever attempted to roll up (or down) your windows and they begin to behave in such a way as you’ve never experienced before?
Generally, if electrical failures begin to happen to your vehicle randomly and unpredictably, then, you’re likely dealing with an alternator that has gone bad (especially if you have an excellent starter battery).
4. Dimming or Flickering Lights
Assuming you’re not using some cheap after-market lights on your vehicle, the illumination from the lights should be steady and solid.
However, if for any reason your OEM lights begin to dim on their own or flicker, you’re likely dealing with a bad alternator.
Your bad alternator status is confirmed if and when the lights improve immediately you rev the motor and they return to their dim or flickering state at idle or low RPMs.
5. Poorly Charged Starter Battery
Sometimes, a bad alternator still manages to provide some juice to the battery – just not enough to make sense. The battery barely charges in such an instance and discharges before you’re aware that it even charged.
Unlike the first instance where the starter battery goes flat completely, here, things aren’t that severe – but the challenge is pronounced enough for you to notice it.
If a new starter battery you’ve installed struggles to start your vehicle (which shouldn’t be the case), then, the alternator is clearly struggling to do its job (and should be changed).
6. Strange (Growling) Sounds
The alternator’s design features bearings which when out, cause the unit to misbehave and eventually, fail.
Before such an eventual failure happens, you’re going to hear growling sounds that are both strange (and familiar) in a curious way.
When this happens (especially in conjunction with other symptoms listed here), your alternator is going out and will need a replacement sooner than later.
7. Engine Stalling or Difficulty Starting
Sometimes, a bad alternator manifests itself by the stalling or an engine, especially an automatic transmission-powered vehicle. If you’re driving and your vehicle simply stalls (in a strange manner, without any logical explanation), then, you’re dealing with a bad alternator, most likely.
This is how it works: the alternator powers most of the electrical components of an engine together with the electronics of the vehicle, with the starter battery assisting.
When, for any reason, the alternator fails to do its job, these electronics/engine components are power starved, and depending on severity, a stall may occur.
A bad alternator can, and will also cause the same symptoms for a vehicle that is stationary by presenting starting difficulties.
What You Can Do
Because a weak starter battery and a bad alternator present similar symptoms, it’s sometimes difficult to isolate one from the other.
This is where dedicated and specialized testing comes in, removing the guesswork and pinpointing exactly where the issue could be: the starter battery, the starter itself, or the alternator.
To accurately isolate a bad alternator and remove guesswork from the equation, you need a dedicated battery tester, capable of testing the battery, starter, and alternator.
I’ve used and highly recommend the Foxwell BT705 and the Ancel BA101.
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Throttle Lan
DIY Mechanic and Freelance Auto Writer