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If it starts to fail, a lot of other things in your car will stop working.
The alternator in your car is responsible for keeping the battery charged and making sure all the other electrical systems in the car have plenty of power to operate.
The alternator produces electricity that is stored in the battery. The battery, in concert with alternator, helps run all the electrical systems and accessories in your car, including the ignition and engine control systems. The alternator is belt-driven by the engine and produces an alternating current (AC). The AC is converted to 12-volt direct current (DC) by the diode bridge.
The alternator keeps things electrically charged and going. If it fails, you’re stuck – and it can go bad slowly or suddenly. If you know the warning signs, you can get the alternator replaced while it’s slowly going bad and avoid being suddenly stranded. Here are some of the things you should know.
If the alternator dies, the battery doesn’t get a charged and rebuild its power storage from any drain it had to cover. When the car is running, the charging system (alternator, voltage regulator) should recharge the battery and provide sufficient electrical power to the vehicle. The battery serves as a backup. If the vehicle requires more electrical power than the charging system – alternator – can provide, the battery covers the difference. This can happen in cold weather, especially if you’re stuck in traffic, in snow or rain. Lots of stop and go, brake lights are on and off constantly, headlights on, heat and defog, interior dash lights, devices like smartphones being charged, radio and any other hi-fi equipment that requires power (boomin’ system), possibly integrated wireless, Bluetooth, onboard computers, entertainment systems like DVD players, games, internet/satellite/cell service connections. It all takes electrical power. The alternator has a pretty tough job.
Related: Have You Checked Your Car’s Electrical System Lately
Know the warning signs of a failing alternator and what to do if it goes out.
The alternator by itself can be the cause of dimming lights, fading radio, and/or stalling.
If the alternator is going bad, you will notice that dashboard lights appear dimmer than usual. Additionally, you might notice that other lights, like the interior cabin light or even the headlights just are not as bright as they should be, perhaps even yellowish. You might notice the lights going dim when some other part of the car kicks in, like the engine cooling fan – and when it stops, the lights return to a somewhat brighter state. This could also be a symptom of other problems within the electrical system that should be checked.
Electrical System Slowing Down
The alternator provides power to the car’s numerous electrical/electronic accessories, from power windows and seats, dash lights, radio and horn to computer chips, GPS and internet connectivity. When things start to go dim, fade out, flicker, or just plain die, it’s a good hint that your alternator is dying, too.
Battery Light or Check Engine Light
Most cars are equipped with a check engine light that comes on to indicate that something is wrong. There is a standard lineup of things that could be wrong if the check engine light comes on, but if the car has a separate battery light, that means something more specific. Some cars have an indicator light on the dashboard titled ALT or GEN, sometimes it is in the outline of a battery to indicate general power or electrical issues (which is where your alternator comes in). Funny how a little light can change your day, or maybe your life. In this case, the alternator or battery (or both) is having a problem. If all the status lights on the dashboard come on, that’s a sure sign of imminent catastrophic failure.
if your car just won’t start, there is most likely a problem in the starting system. If you turn the key in the ignition and all you hear is a click-click-click, or nothing at all, it usually means a dead battery. Why is the battery dead? It’s either old or it’s not being charged by the alternator. The battery’s job is to provide power to the starter to get the car started and all the systems running, including the power/charging system. The battery is not meant to be a long-term power source. Even the best new battery will run down eventually under constant drain with little or no recharge from the alternator. But when the alternator fails, it’s up to the battery to provide electrical power to everything in the car. Diagnosing a dead battery is easy, though. Jump-start the car, remove the jumper cables, let the car run, and wait. If the alternator is dead or weak and not effectively charging the battery, the car will eventually stall. But the best way to determine if the problem is a dead alternator or dead battery is simply to test the battery with a voltmeter, which you can get at most auto stores.
Related: Basics of a Car’s Electrical System
There are parts inside the alternator that spin to produce an electrical current. If one of those parts breaks or wears out, you might hear grinding or whining. The bearings inside the alternator can wear out and cause a lot of noise, like rattling. The alternator pulley spins two or three times faster than the crankshaft pulley, and can wear out, become loose or misaligned, and start to squeal or growl. A worn out bushing, which the alternator is mounted on, can cause strange noises, too.
If the belt on the alternator pulley is slipping or not properly aligned, it can result not only in poor alternator performance and power output, but can cause strange smells. The smell of burning rubber is common in alternator failure situations, so if you smell this in conjunction with strange or less than ideal electrical system performance, you should take your car to a mechanic to have things checked out.