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!

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: Helicopter noise / vibration when driving.

Hi there. The noise is coming from the transmission. The noise could be a gear set inside the transmission with a broken tooth causing the vehicle to shake and sound like a helicopter. I recommend seeking out a professional, such...

Q: Shifter moves in n out of gear without key in ignition or brake pedal depressed

The shifter moving without the brake pedal being depressed is likely caused by the problem with your ignition switch not moving between positions correctly. The shifter interlock is partially controlled by which position the ignition is in, so you will...

Q: Hey there! I can't seem to find the location of my canister purge valve on my 91 Chevy G20 5.7L 350

On these vehicles, the canister purge valve is typically located either on top of, or just in front of, the fuel tank. It has been my experience that they are most commonly found mounted to the top of the fuel...

Related articles

How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.