Alternator & ChargingQuestionCommunity Starter

2024 Ford Mustang — battery dies after the car sits for a weekend

CleanNomad410Community StarterMay 3, 20262024 Ford Mustang GTLas Vegas
2024 Ford Mustang GT, about 29,000 miles. Battery passes a quick test and charging voltage looks normal, but after two or three days parked the car sometimes will not crank. What is the cleanest parasitic-draw test on a modern car that takes time to go to sleep? Mostly looking for the right next step.
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5 replies

NewCarFanCommunity StarterCommunity StarterMay 3, 2026permalink
Don't clear the alert just to make the screen pretty. Leave the alerts on the 2024 Ford Mustang so service can see what you saw. Then you'll know the next fork. This is from a 2024 Ford Mustang in Las Vegas with 29,000 miles. Not gospel, but it saved me a headache. I already checked the easy fluid levels.
TireNomadCommunity StarterCommunity StarterMay 3, 2026permalink
Charge curves lie if you don't match starting SOC and temp. Match starting SOC and battery temp if you're comparing 2024 Ford Mustang charge sessions. Then you'll know the next fork. If it doesn't change the out-the-door or the repair estimate, it's noise. Not interested in a five-hour wait for a shrug.
RoadTripDetailerCommunity StarterCommunity StarterMay 3, 2026permalink
I'd treat 12V warnings as a no-ignore. On the 2024 Ford Mustang, I'd get the 12V/DC-DC side checked even if the traction pack looks fine. Then you'll know the next fork. On “battery dies after the car sits for,” that was the fork that mattered for me. This is from a 2024 Ford Mustang in Las Vegas with 29,000 miles. I'd want a dollar figure or a measured spec, not 'should be fine.' I already checked the easy fluid levels.
CamberDad452Community StarterCommunity StarterMay 4, 2026permalink
I'd treat 12V warnings as a no-ignore. On the 2024 Ford Mustang, I'd get the 12V/DC-DC side checked even if the traction pack looks fine. Then you'll know the next fork. On “battery dies after the car sits for,” that was the fork that mattered for me. Keep sale price, fees, and rate as three different conversations. Climate here is different, so treat that as a local data point. Parking it somewhere I can hear it better next time.
BoxerHauler225Community StarterCommunity StarterMay 4, 2026permalink
Low-voltage gremlins will strand you even with a full pack. Try a second charger before blaming the 2024 Ford Mustang — site sharing and pack temp change the curve a lot. That's where I'd start. If it doesn't change the out-the-door or the repair estimate, it's noise. I'd rather pay for diagnosis than a second guess-repair.
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