When I googled this problem, the most common answer weas dead battery but I bought a new battery a month ago.
I last used my car on Thursday and this morning my car was dead. No lights, radio, odometer, click, nothing. Like I said, I got a new battery a month ago and at the time cleaned the clamps. I didn’t have time to grab my voltmeter this morning so until tonight I don’t know if it is a dead battery or not. One other symptom (maybe) is my car was unlocked [rare] but no doors were open and lights were not left on.
If it is a dead battery, what could cause it to drain so completely in 5 days? Assume I did not leave my headlights or interior lights on.
If it is not a dead battery, what should I check?
Either there’s something wrong with your alternator (jammed, broken belt, just plain doesn’t work anymore), or one of the battery cables isn’t getting a good connection. Make sure you’ve got them clamped to the battery posts as tight as possible.
My girlfriend’s battery did the same thing a couple of months back, and it was because the guy at autozone didn’t tighten the clamp as tight as it needed to be when he installed the battery.
For the particular scenario described – vehicle working fine with (presumably) no symptoms, then not even a hint of electrical power after sitting for 3-4 days – the most likely cause is excessive parasitic drain on the battery. It could be a light somehow left on (can’t tell for sure with no battery power) or a malfunction that caused something to stay on when it normally would be off.
A poor connection is possible, but would have nothing to do with sitting for a few days – it would just be coincidental that it showed up at that time.
Alternator failure, while not impossible, is rather unlikely. If the battery was not being charged, at some point it the battery would be weak to where the car would crank slowly, or maybe not crank at all, but it would be a far way from so dead that nothing electrical worked at all.
I put my money on “infant mortality” of the battery. The failure curve on batteries is steep when new and again when old. It happens.
Of course, if you did leave something turned on, that’s on you. Either way, the battery must be dead.
A charging problem (such as a bad alternator) should cause a dash warning light to come on. The fact that you didn’t see one, and that the car was fine until you parked it for a few days, suggests that it’s not a charging problem.
I once had a drain on my car battery that caused it to go dead in a week. I measured the drain as 600 milliamps. I took a bunch of stuff apart but wasn’t able to find the problem. When I put things back together again the drain was gone. It never came back, and I never did figure out the cause.
One thing you can try (once you have a charged battery in your car) is to use an ammeter to measure the drain. If it’s big enough to cause this problem, try removing the fuses one by one until the drain disappears (or becomes substantially smaller). That will tell you which circuit is causing the drain.
One of our vehicles had this problem one time and it turned out that when you shut the hood, the light under the hood that was supposed to go off stayed on… and promptly drained the battery. Solved it by removing the bulb. Look around for something that is staying on and draining the battery.
I recently had a similar situation. Car started just fine one day, the next it was completely dead. The battery was 7 years old, so it was time for a replacement anyway. When I finished installing the new battery, I noticed that the brake lights were on. Odd. Turns out that the brake light switch had broken.
Not only could the connection be faulty, check the condition of the connectors themselves; within a year of living in South Carolina my connectors rusted through. I bought and installed a new battery before realizing where the problem truly lay.
I had this happen a few years ago – bought a brand-new battery off the shelf, put it in, and within days the car was dead as a doornail. The eventual diagnosis was “the new battery you bought off the shelf was almost completely flat and failed within days,” and the mechanic told me some unscrupulous places leave batteries out for sale for months and years instead of testing them or rotating the expired ones back to the manufacturer.
At least I was able to return the bad battery for a refund, and my car was fixed for the cost of a new (and somewhat more expensive) battery.
I have a Citroen C5 that five minutes after being locked puts itself to sleep.
If I leave a radio or CD on, it waits 45 minutes and then cuts all power until the engine is restarted.
This is naturally to save the battery from being drained whilst the car is not being used.
One guy bought the same model car with an after market stereo fitted, not usually a good idea with these cars but anyway, it turned out that as the car was trying to go to sleep, the radio (not on) would wake it up again and flattened the battery overnight.
He did buy the car like that, very cheaply, as the company that owned it could never diagnose the problem and a flat battery on these cars is a major headache.
OK, tested the battery but first . . .
None of the doors were open and the interior light switches were off. The headlights were off. No hood light but there is a trunk light but no telling if it was on or off of course.
That’s right, after buying it a month ago and after only four days of non-use my battery is down to 3 volts. Is it possible for a parasitical load could take it down that far? I’m assuming it is basically a DOA so I shouldn’t have any problem exchanging it.
This happened to my sister’s car a couple months ago. She got a new battery, and it was dead the next day. We never did notice that the brake lights were always on, but a mechanic figured it out. My first thought when I read the OP was “brake light switch”.
This happened to me about a year ago. I put an ammeter between the negative battery post and its cable to measure the draw (which was comically large, something like 20x the norm for that car) and started pulling fuses to narrow down the source. It turned out to be a short in my aftermarket radio, which was good news because tracking down an electrical short can be a freaking nightmare.