Skip the auto shop - Our mechanics make house calls

Q: Battery or alternator

asked by on

Hello how would I know if my battery is bad or if my alternator is gone...had to get charge ran for a couple of days. Will not keep charge

My car has 177000 miles.
My car has an automatic transmission.

A: This may be a sign of a weak battery, a fai...

This may be a sign of a weak battery, a failing voltage regulator or failing alternator. As you may know, the alternator is responsible for charging the battery while the engine runs by generating amperage and recharging the battery while the engine turns the alternator. The voltage regulator is a unit that regulates the charging of the battery by the alternator. Often times this will result in the alternator allowing too much power to be delivered to the battery resulting in damaging wires and prematurely sometimes destroying the battery. In other cases it may result in the alternator not supplying enough power to the battery, resulting in undercharging the battery or not charging it at all. In some cases when a battery is too weak or damaged, it may no longer hold a charge for any length of time, in which case the alternator may be doing its job, but the battery is just simply too weak to hold a charge. In either case, I would recommend having an expert from YourMechanic come to your location to diagnose your vehicle’s charging system.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Why would the battery and brake light come on for no reason as well as the transmission jerking when accelerating from first to second?

Hi there. Your alternator may not be working properly. If so, turn off all the lights and have the engine running at night. Then from an idle condition, rev up the engine. If the brake and battery light become brighter,...

Q: Loss of power, takes longer to start.

Hi there: Anytime coolant freezes inside an engine, it's typically due to the fact that it's percentage of water was too high. When this occurs, it can cause seals, gaskets and even metallic components to crack or break inside the...

Q: When I start the starts right away but when I put gas it does go it will go like 10mph I donot know what wrong with it

Hello. This can be caused by a few things. If the engine is revving fine but the vehicle does not move then this can be a transmission failure. If the engine is not really even revving well then it may...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the P0052 code means This code is seen when the Engine Control Module (ECM) tries to control the...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.