[Curious Joe]

I have an 08 300, small V6. Replaced the alternator and battery, thought I had it figured out, but I'm having the same issue. No mods, car is stock. No lights left on in trunk or glove compartment, phone charger disconnected and lighter USB disconnected, and stereo powered OFF when I leave the car. Car isn't throwing any codes. Car was fine before engine work was done on it, since then, having this issue. Please help!

First of all, STOP firing the 'Parts Cannon'!

Start from scratch. Fully charge the battery then 'load test' the battery with a load tester of the proper rating as the battery class.

If the battery checks out, then reinstall the clean battery with secure connections. Next, you will need a multi meter that reads mA. Find out what the acceptable 'parasitic draw' is for your car, probably not more than 50mA.

Disconnect the negative cable from the battery and connect the meter between the negative battery post and the clamp. Make sure all doors are closed and everything is turned off for at least 2 minutes.

If you find that you have excessive parasitic draw, you will have to play Sherlock Holmes and track each circuit by pulling fuses/circuit breakers to find the malcontent. Leave meter hooked up to the battery as stated previously.

Good luck.

 

[Curious Joe]

I have an 08 300, small V6. Replaced the alternator and battery, thought I had it figured out, but I'm having the same issue. No mods, car is stock. No lights left on in trunk or glove compartment, phone charger disconnected and lighter USB disconnected, and stereo powered OFF when I leave the car. Car isn't throwing any codes. Car was fine before engine work was done on it, since then, having this issue. Please help!

One more 'heads up' - incredibly simple. Affects some cars but not all. Should be standard practice anyway.

Whenever you connect-disconnect a motor vehicle battery:

1. ALWAYS disconnect the negative cable first.

2. ALWAYS reconnect the the negative cable last.

3. Same procedure with jumper cables - booster box, etc.


Most modern cars/trucks will keep the power on for up to a minute after turning the key off, to briefly operate the windows, lights, radio, etc. Sometimes this function gets out of whack and the very first thing many techs will do (after checking the battery) is to disconnect-reconnect the battery in the manner described, as it may help a stubborn electrical system reorient itself.

Worked for me on a 2005 Mustang GT - FoMoCo even had a service bulletin about it that dealers apparently didn't read....

Worth a try.