Common problems
Car electrical problems: battery drain, alternators and warning lights
Most car electrical problems come down to four things: a weak battery, a failing alternator, a drain that empties the battery while the car is parked, or a fault in the wiring or a control module. Some are just a nuisance. Others, like stalling, loss of lights or a fire risk, are safety issues that you should act on quickly.
When an electrical problem is a safety problem
Modern vehicles depend on electricity for almost everything, including engine control, power steering, brakes, airbags and lights. Get help quickly if you notice:
- the engine stalling or the car shutting down while driving
- headlights, brake lights or turn signals failing
- the airbag, ABS or power steering warning lights coming on
- a burning plastic smell, smoke or melted wiring
- fuses that blow again after being replaced
Battery problems
Car batteries wear out. Many last around three to five years, and heat tends to shorten their life. Signs of a weak battery include:
- slow cranking when you start the engine, especially on cold mornings
- the car needing a jump start
- a battery warning or "low battery" message
- swelling, leaking or heavy corrosion on the terminals
Many auto parts stores and repair shops can test the battery and charging system. A fully charged 12-volt battery typically reads about 12.6 volts with the engine off.
Battery drain while parked
If a healthy battery goes flat after the car sits for a day or two, something may be drawing power when it should not. This is called a parasitic drain. Common causes include:
- a light that stays on, such as a glove box, trunk or vanity mirror light
- aftermarket accessories, like dash cams, alarms or chargers left plugged in
- a control module that does not "go to sleep" after the car is locked
- a faulty relay or switch
Some vehicles have known drain problems, sometimes fixed by a software update under a technical service bulletin. A shop can measure the drain and track down which circuit is causing it.
Alternator problems
The alternator charges the battery and powers the car while the engine runs. When it fails, the car runs on battery power until the battery is empty, then stops. Warning signs:
- battery or charging warning light while driving
- headlights or dashboard lights dimming or flickering
- electrical features working slowly or cutting out
- a whining or grinding noise from the engine bay
- a burning smell, sometimes from a slipping belt
With the engine running, a healthy charging system typically shows roughly 13.5 to 14.5 volts at the battery, though some newer cars vary this on purpose. If the battery light comes on while driving, turn off what you do not need and head for a safe place or a shop. You may only have a short time before the car stops.
Wiring and connector faults
Damaged wiring can cause intermittent problems that are hard to track down: lights that flicker, features that work one day and not the next, or warning lights that come and go. Common causes are corrosion from water leaks, chafed wires, rodent damage and poor aftermarket installations.
Module failures and warning-light storms
Vehicles have many computer modules that talk to each other over a network. When one fails, or a connection or the voltage supply is poor, you can see a "warning-light storm": many warning lights and messages at once, such as ABS, traction control, airbag and steering lights all together.
This often looks worse than it is. A common cause is a weak battery or a poor ground connection, because modules behave strangely when voltage drops. But it can also be a failing module. Do not ignore it: if the warnings involve brakes, steering or airbags, those systems may not be working.
Infotainment, cameras and screens
Frozen screens, rebooting infotainment, a dead backup camera or Bluetooth that keeps dropping are among the most common complaints about newer vehicles. Many are fixed with software updates. A backup camera that does not work is more than an annoyance: rear visibility cameras are required equipment on new vehicles, and failures have led to recalls.
What to do
- Note what happens and when. Write down the lights and messages, or take a photo of the dashboard. Note whether it happens cold, after rain or over bumps.
- Test the battery and charging system. It is quick, often free at parts stores, and rules out the most common cause.
- Check for recalls. Use our VIN check. Wiring, module and fire-risk problems are often recalled.
- See what other owners report. Browse electrical problems, or your own model's page, such as 2014 Jeep Grand Cherokee electrical.
- Ask about software updates and bulletins. Many electrical and infotainment issues have a known fix. See TSBs and goodwill repairs.
- Use a shop with good diagnostic equipment. Intermittent electrical faults take time and the right tools to find.
Typical repair costs
These are typical rough ranges that vary widely by vehicle and location.
- 12-volt battery: often about $150 to $350 installed, more for some vehicles.
- Alternator: often about $400 to $1,000 or more.
- Tracking down a parasitic drain or wiring fault: depends on how long it takes, from about an hour of labor to much more.
- Control module: from a few hundred dollars to well over $1,000, plus programming.
Report it
If an electrical fault caused stalling, lights failing, a warning about brakes or airbags, or any sign of fire, file a complaint with NHTSA. And share your experience here so other owners can recognize the problem sooner.
Questions and answers
Why does my car battery keep dying?
The most common causes are an old battery, a failing alternator or a parasitic drain from something that stays on while the car is parked. A shop can test each one.
How do I know if it is the battery or the alternator?
If the car is hard to start but runs fine once started, the battery is often the cause. If the battery light comes on while driving or the lights dim, suspect the alternator. A charging system test will tell you.
Why are all my warning lights on at once?
A weak battery or poor ground connection can make many modules report faults at once. A failing module is another cause. Get it checked, especially if brake, steering or airbag lights are on.
Can electrical problems cause a car fire?
Yes. Short circuits and overheating wiring or modules can start fires, and some have led to recalls. Act quickly on burning smells, smoke or fuses that keep blowing.