Today’s cars use two different sources of energy: mechanical and electrical. Your engine produces mechanical power through combustion, providing the power needed to move your wheels. Meanwhile, a number of other systems, from your headlights to your radio, rely on the electrical power provided by your battery.
These two systems interact through the alternator, which converts mechanical energy into electrical energy, keeping the battery charged. When an alternator stops working properly, it can cause a variety of problems. Before that happens, though, you’ll likely encounter one or more of these seven signs of a bad alternator.
7 Signs Of A Bad Alternator
1. Dim or Overly Bright Lights
Your headlights might dim or brighten unevenly and perhaps even flicker. This could mean the vehicle’s alternator has trouble delivering consistent power. One way to check is to rev the engine. If your headlights brighten at a higher RPM and then dim when you take your foot off the pedal, your car alternator definitely has issues.
2. Dead Battery
A dead battery almost always lies behind a car that won’t start. If you jump-start the car and it runs correctly, the problem likely stems from the battery itself. In some cases, the battery may have just become drained for instance, if you forgot to turn your lights off. In such cases, jumping the battery and allowing your car to run for a few minutes fixes the problem.
If your car remains running once jumped, yet won’t turn over the next time you try to start it up, you may need a new battery. Because the car continues to run once started, you know that the alternator remains capable of performing its function. Instead, the battery does not seem capable of holding a charge with the engine off.
If your engine dies again within seconds or minutes of jumping the battery, the fault probably lies with your alternator. In fact, your alternator may have died completely. Installing a new battery may relieve the problem for a short time. Yet, once the new battery has discharged its power, you’ll be stuck with a car that won’t start again.
3. Electrical Issues
A dying alternator can lead to a wide range of other electrical issues. Generally speaking, such issues manifest as an inability to perform at normal power. For instance, you may notice that your headlights seem dimmer than usual or even that their brightness fluctuates inexplicably.
Other signs include dash and dome lights that may also flicker or appear dim. Automatic windows may open and close much more slowly than usual. Or, your radio and/or entertainment centers may shut themselves down periodically.
4. Engine Stalling
A dead alternator almost always leads to a car that won’t start. Yet, before things get to that point, you may experience a range of other problems. A faulty or dying alternator may only work in fits and starts. As a result, the alternator may not have what it takes to keep your battery fully charged — even with your engine running.
As a result, you may find your car stalling out at odd times. The immediate cause of such stalling often lies with the fuel injectors, which require electricity to do their job. If a faulty alternator fails to keep your battery consistently charged, the fuel injectors may not fire, causing your engine to stall.
5. Growling or Whining Noises
Cars make a ton of odd sounds some are harmless while others can indicate serious mechanical problems. If you ever hear growling or whining noises coming from under the hood, you could have alternator problems, which should be checked out by a professional ASAP.
This growling or whining sound happens when the belt that turns the alternator’s pulley becomes misaligned or rubs against the side of the pulley. You may also hear this sound if the bearings that spin the rotor shaft are going bad.
6. Smell of Burning Rubber or Wires
A foul odor of burning rubber or wires could indicate that parts of your alternator are starting to wear out. Because the alternator’s drive belt is under constant tension and friction and because it’s close to the hot engine it may wear out over time and emit an unpleasant burning rubber smell.
Similarly, if your alternator is being overworked or if it has frayed or damaged wires, you may smell a burning odor comparable to an electrical fire.
An overworked alternator tries to push too much electricity through its wires, causing them to heat up unsafely. Damaged wires also create resistance to the flow of electricity, causing the wires to heat up and emit a foul odor.
7. Battery Warning Light on Dash
When the battery warning light pops up on the dashboard, it’s commonly mistaken to be a battery-specific issue. However, the battery warning light indicates that there could be a problem within the wider electrical system of your car, including the alternator.
Alternators are designed to work at a specific voltage, typically between 13-14.5 volts. If your alternator is failing, its voltage may drop below capacity, causing the battery warning light to appear on your dash. Similarly, the battery light will also appear if the alternator is exceeding its voltage limit, depending on how much stress it is under.
Depending on the electrical load from your car’s accessories (headlights, wipers, radio, etc.), you may see the battery warning light flicker on and off as the alternator fluctuates in and out of its intended voltage capacity. While this may seem like a minor annoyance, it’s better to bring your car in for an alternator inspection rather than wind up stuck on the side of the road.
If you have noticed any of these symptoms, seek professional assistance as soon as possible. Even if your car continues to run, the alternator may soon fail completely.
7 Signs of a Failing Alternator
1. Dim or Overly Bright Lights.
2. Dead Battery.
3. Slow or Malfunctioning Accessories.
4. Trouble Starting or Frequent Stalling.
5. Growling or Whining Noises.
6. Smell of Burning Rubber or Wires.
7. Battery Warning Light on Dash.
A car can only run for a short time with a failed alternator. The alternator charges the battery when the engine is running and, once the battery is depleted, the vehicle will die and fail to restart.
If the engine starts but dies immediately, your alternator probably isn’t keeping your battery charged. If a jump-starts and keeps your car running, but the car can’t start again off of its own power, a dead battery is probably your answer.
It depends if a repair is possible. If not, you’ll have to have it replaced, which can run between $500 to $1,000 (including parts and labor). Otherwise, for something simple like replacing an alternator belt, expect to pay about $100-$150 (not including diagnosis).
A common sound made by failing alternators is a very high-pitched whining noise that you’ll hear when the engine is running. When the RMPs increase, such as when you accelerate, you’ll hear the noise get higher in pitch as the pulley spins faster.