Q: My car wouldn't start after battery was just replaced my car cd player is running after I turn the car off

Your CD player definitely should not be running after the key is off and out of the car. It will certainly drain your battery. So the good news is you can be reasonably certain about what is killing your battery. I would remove any CD’s from the player and see if it still spins with the key out of the car. If you need to go a step further, you will need to disconnect the power wire to the stereo. It is located at the back of the stereo and this will require some dash disassembly to access the rear of the radio.

You will want to disconnect the stereo overnight to see if the battery dies. A quicker more accurate way of testing for a draw, which is what this is called, is to use an amp meter at the battery to confirm the stereo is the source of the draw. Most multimeters have amp settings that can be used up to a ten amp draw. You will need to connect the leads of the multimeter inline with the positive battery cable. Do not turn the key on while the multimeter is inline with the battery. The current will blow the fuse in the multimeter then you won’t be able to complete the test. Also, you will need to wait somewhere between ten minutes and an hour for all the modules in the car to go to sleep. Modules that are on will draw current until they go to sleep. You are looking for a draw of more than a half of an amp continuous.

With the multimeter connected, disconnect the radio connector and see if the draw goes away. You will see this reflected in the multimeter amperage reading. This draw test can be used to locate any draw that may be occurring. If you find the radio is not the culprit, you should then begin removing fused one at a time to see what is causing the draw. When the draw goes away after removing a fuse, something on that fused circuit is causing the draw.From there you will need to study a wiring diagram to see what is on that circuit.

Of course, all this takes an understanding of electricity to do these test. If you should need assistance with this, I recommend the following inspection; Battery is dead inspection from a certified technician from YourMechanic.

Good luck!