7 Signs Your Alternator Is Failing (Don't Get Stranded)
Learn the warning signs of alternator failure before you get stranded. Understand how to tell the difference between alternator and battery problems.
Your Alternator Keeps Everything Running
While your battery starts your car, the alternator keeps it running and charges the battery while you drive. When your alternator fails, your car will eventually die—often at the worst possible time.
How an Alternator Works
The alternator is driven by a belt connected to your engine. As it spins, it generates electricity to:
- Power all electrical systems while driving
- Recharge your battery
- Maintain proper voltage throughout the vehicle
7 Warning Signs of Alternator Failure
1. Battery Warning Light
The battery-shaped warning light on your dashboard doesn't just indicate battery problems—it monitors your entire charging system. If this light comes on while driving, your alternator may be failing.
2. Dim or Flickering Lights
When an alternator starts failing, it can't supply consistent voltage. You might notice:
- Headlights dimming or brightening randomly
- Dashboard lights flickering
- Interior lights acting erratically
3. Dead Battery (Again and Again)
If you keep jump-starting your car and the battery dies again after driving, your alternator likely isn't charging it. A healthy alternator should keep a good battery charged.
Quick test: After jump-starting, disconnect the jumper cables. If the car dies immediately, the alternator is likely dead.
4. Slow or Malfunctioning Electronics
When voltage drops, electronics get sluggish:
- Power windows move slowly
- Radio cuts out or resets
- Heated seats work intermittently
- Dashboard instruments act strange
5. Strange Sounds
A failing alternator can make:
- Whining or buzzing from voltage irregularities
- Grinding from worn bearings
- Squealing from a slipping belt (might be a belt issue, not the alternator)
6. Burning Smell
A burning rubber or electrical smell could indicate:
- Slipping alternator belt (overheating)
- Overworking alternator generating excess heat
- Melting wires from voltage irregularities
7. Stalling or Difficulty Starting
A failing alternator can cause:
- Hard starting (not enough charge to battery)
- Stalling while driving (insufficient power to ignition system)
- Random power loss
How to Test Your Alternator
With a Multimeter:
- Set multimeter to DC voltage
- With engine OFF: Battery should read 12.4-12.7 volts
- With engine RUNNING: Should read 13.8-14.4 volts
If the running voltage is below 13.5 or above 15, your alternator has problems.
Visual Inspection:
- Check the drive belt for wear and proper tension
- Look for loose connections
- Check for burning smells
Alternator Lifespan
Most alternators last 7-10 years or 100,000-150,000 miles. However, extreme heat (like NYC summers) and electrical load can shorten this.
Alternator Replacement Cost
Expect to pay $400-$900 for alternator replacement, depending on your vehicle and labor involved.
Can You Drive With a Bad Alternator?
Technically, yes—until your battery dies. Once the battery is depleted (usually 20-30 minutes of driving without a working alternator), your car will stall and won't restart.
Don't risk it. Getting stranded in NYC traffic with a dead car is dangerous and stressful.
Mobile Alternator Service in NYC
NYC Mobile Auto Assist can diagnose charging system problems and replace your alternator at your location. Don't wait until you're stranded—if you notice any warning signs, call us for a charging system check.
Need Professional Help?
NYC Mobile Auto Assist provides expert mobile mechanic services throughout all five boroughs. We come to you!