The battery dies if the car sits a few days
Something is staying awake after you lock the car. A module that never sleeps, a glove box or trunk light that stays on, an add-on alarm or stereo, or a charging port with something plugged in. A battery that has lost capacity in the heat makes it worse, because it has less reserve to lose. Sometimes it is just a battery that is done, and sometimes it is the alternator not fully charging on short trips.
What to do right now
- 1Unplug everything from the 12V outlets and USB ports: dash cams, chargers, GPS units, plug-in air fresheners. Dash cams with parking mode are a very common cause.
- 2Check that the trunk, glove box, and vanity lights actually shut off. Close the doors and look through the windows at night.
- 3Note how long it takes. Dead overnight is a big draw or a bad battery. Dead after four or five days is a small draw or short trips that never fully recharge it.
- 4Do not just buy another battery. If the draw is still there, the new one dies the same way and you have paid twice.
What it usually is
Battery replacement
We load test the battery first. A battery that has lost half its capacity in the Miami heat goes flat from a normal draw that a healthy battery would shrug off.
See the serviceElectrical repair
A parasitic draw test with a meter on the battery lead, then pulling fuses one at a time until the draw drops, tells us exactly which circuit is staying awake.
See the serviceStarter and alternator
An alternator with a bad diode can drain the battery overnight, and one that charges weak never catches up on short trips around Miami Gardens.
See the service