Long story short – new battery installed in wife’s car Monday evening. Car’s been started 7 or 8 times since, started up like a champ each time. This morning, I’m at work and my wife claims car won’t start and “battery light is beeping”. She held her phone up to the instrument panel, and something is/was beeping. It’s absolutely confirmed that no lights, radio, etc. were left on overnight – nothing like that is the issue.
Father-in-law passed by my house and looked at wife’s car’s battery, declared it to be dead and blamed the alternator as the likely culprit. I have not talked to my FIL, getting this second hand from my wife.
FWIW, it’s a 2003 Ford Taurus. Anybody ever run into a similar issue? TIA for any advice.
The battery is still ok. If you get the alternator replaced (the most likely culprit) and charge the battery, you should be good to go. Again, this is common, but not always the issue. Gotta start with the likely things first. A decent shop should be able to check the alternator and confirm.
Your FIL is correct the alternator is the most likely culprit. Not the only one mind you, but the most likely.
You can either:
[ol]
[li]Throw parts at it[/li][li]Pay someone to check it out and throw the right part at it the first time[/li][li]Check it out yourself (assuming you have a voltmeter) and throw the correct part at it.[/li][/ol]
The alternator is basically a generator which converts the mechanical energy of the engine into electrical energy. This electrical energy is used for lots of things in the car - powering the spark plugs, keeping the various lights lit, powering the radio, and charging the battery. When the alternator is running correctly, the battery is doing nothing to power the car, and can in fact be disconnected without the car dying. In this normal domain of operation, the battery is only needed for starting the car - the electrical energy of the battery is used to start the mechanical parts of the engine moving, and to power the spark plugs. Once the engine starts running, the alternator takes over again.
If the alternator is dead, but the battery is fully charged, the car can and does use the electrical energy provided by the battery to run all the electrical requirements of the car. However, the battery is now being drained the entire time the car is running, and there’s nothing going to recharge it. You can often notice this happening because the lights begin to dim in the car as the battery discharges.
It can happen where the battery has enough power to continue running the car, but after it’s been turned off for a while, it doesn’t have enough power to start the car again. This happens for 2 reasons - the power required to start the car is much higher than what’s required to keep it running, since you’re using electrical energy to get big pieces of metal in motion, and there’s usually a small current flow even when the car is turned off for things like the radio memory, remote key fob receiver, alarm systems, etc.
True, and it can ruin the alternator or certain electronic devices to do so. It’s not 1960 anymore, and we don’t have DC generators on cars (that’s when it was safe to do this). Do yourself a favor, everyone, and DO NOT run the engine with the battery disconnected.
The problem could be an alternator that’s not charging, or it could be an electrical drain on the battery. And as Rick said, you can either have it diagnosed by testing, and have confidence that the indicated repair will fix it, or you can diagnose by parts replacement, where if your first guess is right it will save you money but if you guess wrong it can get very expensive.
Put another way – assuming a brand-new fully-functional alternator and a brand-new fully-charged battery (I understand some are sold undercharged when new). No lights left on, no electronics left on. The alternator and battery both pass diagnostics by three different super-reputable shops with flying colors.
Given all that … is there something that could conceivably kill a battery in less than two days of light driving?
The alternator charges the battery, so if the alternator and battery are good, nothing will kill the battery*. If the alternator is bad, then everything electrical is running off the battery and it doesn’t take much to drain it. Just starting the car a few times may do it.
Ok, some things can but I don’t suppose your wife has a winch that draws 400 amps on her Taurus.
No, but it has headlights that draw 10 amps, and they can drain the battery enough to cause a no start in a matter of hours. There are a number of things that could cause a drain big enough to cause a no start from sitting overnight.
But he said “brand-new fully-functional alternator and a brand-new fully-charged battery (I understand some are sold undercharged when new). No lights left on, no electronics left on.”
A sticking relay, a computer that does not shut down, a trunk light that stay on can all drain a battery overnight.
I once had a car that would drain the battery night after night. I tested for a draw every way I knew how. NO draw, but the next morning the battery was dead.
After a hour or two of exhausting every possibility I was standing next to the car looking at the parking place outside where it had gone dead the night before, and I asked myself the question “What is different out there, than in the shop here?”
I came up with:
[ol]
[li]One is outside, one is inside[/li][li]windows rolled up[/li][li]door locked[/li][/ol]I eliminated #1 out of hand. I rolled up the windows to test #2, nothing.
Then I locked the car, and found the lock relay was sticking causing a 10 amp draw.
The bottom line is this:
Either the battery is in fact bad, the alternator is in fact bad, or there is a draw. There is no fourth choice.
