Your car fails to start or stalls frequently. The interior lights are dim. Electrical accessories constantly malfunction. Is the battery or alternator the problem? Here’s how to tell.
If it’s the battery…
Your Car Will Take Unusually Long To Start – or Not Start At All
If the battery is at fault, your car will take longer than usual to start. Of course, if the battery’s dead, your car won’t start at all. However, if your car works fine after jump-starting but fails to start again afterward, the battery is almost certainly the culprit.
Electrical Components Will Malfunction
The battery is the sole source of electrical power when your car engine is off. If it develops a fault that diminishes its power output, components of your car’s electrical system will inevitably malfunction – headlights and dashboard lights will be dimmer than usual, for example, while power windows will operate sluggishly.
There May Be Other Battery-Related Problems
If you’re still unsure if the battery or alternator is the culprit, a physical inspection may help settle matters. Check if the battery terminals are corroded. Corrosion impairs the flow of electricity, making it harder, if not impossible, for the battery to get a proper charge. Is your battery constantly exposed to extreme temperatures? Check to see if it is warped. Extreme temperatures can trigger chemical changes that cause batteries to swell, buckle, and ultimately malfunction. Notice a smell like rotten eggs when you pop the hood open? It’s a sign that the battery is leaking, a sure indicator of malfunction. Something else you need to consider is the effect of age; batteries tend to hold less and less charge over time and may need to be replaced every three to five years.
If it’s the alternator…
Your Car Will Stall Frequently and Have Trouble Starting
A malfunctioning alternator will be unable to charge your battery properly. In turn, this means the battery won’t have enough power to turn over the engine. Wondering how to tell if the issue is the battery or alternator in this case? If your car stalls almost immediately after a jump-start, the alternator is the likely culprit; ditto if your engine stalls frequently when you are driving.
Your Car Will Have Myriad Electrical Problems
Unsurprisingly, a faulty alternator causes a multitude of electrical problems. The character of these faults is somewhat different from battery-related electrical problems, so you will probably be able to tell them apart in many cases. For instance, when the alternator is faulty, headlights usually become brighter at higher revs and dim when you take your foot off the gas. With a bad battery, the light output is sub-par but even. Other common alternator-related problems include a dead battery, a malfunctioning speedometer, and slow-rolling power windows.
There May Be Other Problems As Well
A burning smell is another common sign of a faulty alternator. The cause is usually a damaged alternator belt or frayed wires. Your car may also make growling or squeaking sounds, and these may get louder when the heater or sound system is on. The culprit is usually a misaligned alternator belt rubbing against the alternator pulley. In some cases, the dashboard battery light may keep flickering on and off as different components power up or down, a sure sign that the alternator is unable to provide adequate power consistently.
Closing Thoughts
This quick cheat list can help you tell apart battery problems from alternator faults. However, you should always see professionals if your vehicle has an issue. If it turns out your battery or alternator is defective, said professionals can help you find a suitable solution. All the best!