Skip the auto shop - Our mechanics make house calls

Q: Alternator, Serpentine belt, or battery?

asked by on

So, my car had died about a month ago after having about a week or so of really soft starts. I got it jumped, I unhooked the positive from the battery and it ended up staying on. The internet told me this means it's not the alternator. So I buy a new battery from Autozone and the car starts working normally again.

Now 2 days ago, so a month from my purchase of the last battery, I was driving home and the engine shut off while at a stop light. It wouldn't turn back, it wouldn't even crank. I got it into neutral and pushed it to the side and got towed home.

We tested a few things, if it would turn at all (it didn't) and if anything in the car worked (it didn't). Not even the electric windows would roll up.

So (yesterday) we jumped it, left it on for about 30 seconds and it died. We bought a new battery and it started but i unhooked the positive battery cable and it died instantly.

Is it just a bunk battery or alternator issues and could it possible be the serpentine belt?
My car has an automatic transmission.

Hi there. It sounds like the alternator has failed. What the internet didn’t tell you was that the alternator’s voltage during idle and load as well as its output amperage during both conditions needs to be tested to properly determine the state of health of the alternator. This is not to say that what tests good today will not fail tomorrow, but it means that at that moment it is operating properly. Your alternator may have been losing its charging capabilities when you checked the first time, but was charging enough to keep the engine running. I suggest having a qualified technician perform an inspection to avoid replacing unnecessary parts. Your Mechanic has several available technicians that can assist you with an electrical problems inspection.

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!
  1. Home
  2. Questions
  3. Alternator, Serpentine belt, or battery?

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: Transmission slipping

The transmission was possibly putting some sort of increased load on the engine. You may want to have the fault codes read out of the engine and transmission. Volkswagen has a TSB out for an improper shift from 2-3 gear,...

Q: Car floods bad when cold. If I give it a little gas it jumps and jerk and if I mash it on down it takes off. I've replaced the O2 sensor and coolant temp sensor.

This may be related to a dirty or faulty idle air control valve. This is a unit that reads the air intake at low or idle speeds and relays this information to the computer which then makes adjustments to fueling....

Q: Power locks not working right

This is often related to a malfunctioning door lock actuator, a blown fuse or a faulty power door lock switch. When you use the door lock switch in the car it sends a signal to a relay which then activates...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
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...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...