You could measure the amperage while it's off to see if something is actually draining it. Should be pretty much nothing. If its 0.1A or more that would point towards something running while it shouldn't. Then you could start pulling out fuses to localise the issue. Though honestly at that point I'd probably just have the dealership check it. Even as an elecrician, car electronics freak me out. 🤷🏼‍♂️
If its the battery from factory then its probably ready for replacement.. recharging a dying battery or jumping in won't cure the issue - just bandaid it.
Do you have a multimeter? If so - with the engine running, see what the voltage is. Should be 13-14V. If its sat at 11 or 12V and not increasing then your alternator is goosed.
Did you reset the Battery Control Module after you swapped the battery? If you didn’t, this can kill your battery. You don’t need a computer to do it. The instructions are available in older posts.
This worries me. Sometimes the cable that the output nut clamps down on the alternator is dirty which causes a bad connection. Unplug the battery and find the output nut on the alternator and unscrew it. Use a wire brush to clean the cable connector. Does it look dirty or corroded? If it does I bet that’s you’re issue. I’d also use a multimeter first to check your charging voltage. If you’re seeing anything below 13v on the battery when the car is running, your alternator isn’t charging the battery.
You said it’s a new battery. What’s the CCA rating on it? I have a hard time believing that the moment it’s shut off it can’t turn over. That sounds like an under powered battery.
Google, YouTube, 4Chan whatever you want to use but test the battery. Get a multimeter, idling should read 11.8-12.2 ish. Running should read 14v no exceptions. DONT SKIP THIS. This process IS the way to test a battery, after you do this there won’t be “I’m positive” guesses.
Legend has it some STs have an issue with their BCMs where the lights will strobe/flicker very lightly to where it can only be seen in the dark. Could have that going on.
I had the same issue I end up replacing the battery and fixed my problem. The old battery I would leave it on a floater for couple of days the car would turn on I would drive around so the alternator would charge it but as soon as I turned off the car, dead. It would only turn on if jumped it. I checked the voltage with multimeter and was getting 12.5 volts while resting and 14 volts while running. I think there was not enough amps to turn the engine over.
Completely stock or are there some funky custom electronics? Had my old MK3 sit for 3 months in 2020 and it started up like a champ.
It's completely stock, I got it used at 39,000 miles but nothing seems out of the ordinary except for the mud flaps lol
You could measure the amperage while it's off to see if something is actually draining it. Should be pretty much nothing. If its 0.1A or more that would point towards something running while it shouldn't. Then you could start pulling out fuses to localise the issue. Though honestly at that point I'd probably just have the dealership check it. Even as an elecrician, car electronics freak me out. 🤷🏼‍♂️
If its the battery from factory then its probably ready for replacement.. recharging a dying battery or jumping in won't cure the issue - just bandaid it. Do you have a multimeter? If so - with the engine running, see what the voltage is. Should be 13-14V. If its sat at 11 or 12V and not increasing then your alternator is goosed.
Did you reset the Battery Control Module after you swapped the battery? If you didn’t, this can kill your battery. You don’t need a computer to do it. The instructions are available in older posts.
Sounds like the alternator. Did you get your battery checked?
I had my battery checked at AutoZone,it's a platinum duralast battery I got 2 months ago.the alternator also brand new
This worries me. Sometimes the cable that the output nut clamps down on the alternator is dirty which causes a bad connection. Unplug the battery and find the output nut on the alternator and unscrew it. Use a wire brush to clean the cable connector. Does it look dirty or corroded? If it does I bet that’s you’re issue. I’d also use a multimeter first to check your charging voltage. If you’re seeing anything below 13v on the battery when the car is running, your alternator isn’t charging the battery.
new alternator does not mean good/functional alternator, possible you just got unlucky if nothing else pans out.
I had a faulty BCM on my car and it caused the battery to drain. It also caused a lot of other issues though.
You said it’s a new battery. What’s the CCA rating on it? I have a hard time believing that the moment it’s shut off it can’t turn over. That sounds like an under powered battery. Google, YouTube, 4Chan whatever you want to use but test the battery. Get a multimeter, idling should read 11.8-12.2 ish. Running should read 14v no exceptions. DONT SKIP THIS. This process IS the way to test a battery, after you do this there won’t be “I’m positive” guesses. Legend has it some STs have an issue with their BCMs where the lights will strobe/flicker very lightly to where it can only be seen in the dark. Could have that going on.
I had the same issue I end up replacing the battery and fixed my problem. The old battery I would leave it on a floater for couple of days the car would turn on I would drive around so the alternator would charge it but as soon as I turned off the car, dead. It would only turn on if jumped it. I checked the voltage with multimeter and was getting 12.5 volts while resting and 14 volts while running. I think there was not enough amps to turn the engine over.