When your car won’t start, it’s reasonable to blame it on the battery. However, if you check out your alternator, you may find your battery is innocent.
Let’s go over how to tell the difference between alternator vs. battery problems to help you make quick work of the diagnosis and repair so you can get back on the road.
WHY CHECK YOUR ALTERNATOR
The alternator is an essential part of moving your vehicle. You’ll find it underneath the hood of your car, typically bolted to the engine. The alternator turns mechanical energy into electrical energy. Using a stator and rotor, an alternating current (AC) is formed and then transformed into a direct current (DC), which charges the battery.
Your car will only run for a short period if its alternator is in bad shape. Without a working alternator, your car’s battery can’t charge and, eventually, the car won’t start at all.
If you continue driving with a bad alternator, you can damage crucial electrical components like the water pump, power steering, and fuel pump. A weak alternator can also cause your engine to stall, which can be very dangerous if you’re driving at high speeds or in heavy traffic.
To avoid damaging your vehicle or putting yourself in danger, assess your alternator as soon as you notice symptoms that it could be failing.
SIGNS YOUR ALTERNATOR IS FAILING
Some common symptoms of a bad alternator include:
- frequent stalling or trouble starting
- growling or squealing noise
- dim or overly bright lights
- battery warning light on
- burning rubber smell
Some of these symptoms are similar to the symptoms of a dead battery. If your car shows any of these signs, start by assessing your battery. Car alternators usually last seven years, whereas batteries last three to five years. Because of this shorter life expectancy, it’s fair to assume your battery will fail more often.
We have a guide on how to examine your battery here. Always wear gloves when touching your battery. Use a multimeter or battery tester to confirm whether your battery is above 12.4 V or not. If the voltage is low, charge your battery with a battery charger or jump starter.
If the battery passes the test but your car is still having problems, it’s time to critique the alternator. If the battery is dead, still assess the alternator in case both are at fault.
INSPECTING THE ALTERNATOR
If you’re new to automotive DIYing, have your alternator tested by a professional. You can get this done at one of our 650 SHENSHUAI AUTOPRO service centres. For those with mechanical experience, you can test your alternator yourself.
With the ignition on, use a multimeter to check the charge at the alternator output. Test the output at various RPMs (e.g., when the engine is at idle speed and at 2,500 rpm.) Sometimes, the regulator is faulty, and the alternator output may be affected by output crossing the 20 V range. This would indicate a bad regulator, which can also damage the battery. If it’s in the 13 to 15 V range, your alternator is fine, and you need a new battery.
If your alternator fails this test, it may need to be replaced.
ALTERNATOR MAINTENANCE TIPS
Like many parts of your car, your alternator will perform its best with regular maintenance. When you assess your alternator, carefully clean away debris with a vacuum or microfiber cloth. If it looks really dirty, have it professionally cleaned.
Over time, the alternator’s drive belt can become loose or worn. Check the tension of the belt every three to six months and have a professional adjust it as needed.
As your alternator gets close to the end of its lifespan, consider preemptively changing it to avoid any unexpected failures.
If you have any questions about your car’s alternator, visit a SHENSHUAI Auto Parts store to speak with an expert. You can also check out all the electrical system products available on shenshuaiautoparts.com.
