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Q: new battery is draining within 24 hrs, everything checks out ok by mechanic who is still testing more parts

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Last week went to start car & it was dead, no sounds at all. Roadside service tech jumped battery so as to move it out of my garage & onto tow truck & towed to mechanic who said 3 yr old battery was the problem, so he sold me a new one. I picked up car & went out for several hours, then home, car was fine. Next day. again car is completely dead & was retowed back to mechanic. He checked out alternator, starter, ignition, fuses and then checked "Light Control Module" & tested a new one overnight, but next day he called to say that was not the problem either, so he is continuing to check what else. Can you please give me some hints of where else to look for problems as the mechanic has my car for several days now & I need it back asap. Thank you so very much for your help..

My car has 95000 miles.
My car has an automatic transmission.

Hey there, It sounds like you may have a case of parasitic draw. This is when a system stays active and slowly draws battery power when the car is shut off. This can also be caused by the charging system not having proper output. In either case it is entirely possible the drain, over time, had killed the battery. Batteries do not like to be drained completely and will not always recover, leading to the need for replacement.

Parasitic draw cases can be notoriously difficult to diagnose. The circuit with the draw must first be identified, then once the circuit that the problem is on is identified, it becomes easier to diagnose. The draw can be caused by many things, shorted to power wiring, aftermarket stereo and alarms, ECM failing to go into sleep mode and etc... This particular situation may take the mechanic some time to diagnose but if problems persist the certified technicians at YourMechanic would love to help you figure out why your car does not start.

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