Car Radio Draining Battery Problem. 02 Tahoe that I have had for several mos. My mechanic did a parasitic load test and found that my aftermarket stereo was responsible.
If the unit is can bus decoder controlled device such as Volkswagen device you may found out that the red ACC wire is comes out from the can bus box and goes to the radio instead of direct connect with the original car connector. Remember that the drain doesnt have to take your battery to zero overnight just low enough for it to not start. Newer cars should be able to play radio easily for at least 10-15 hours without draining your battery.
This will cause your stereo system to work improperly.
Heres an article that might help with troubleshooting. So when the car is turned off the radio still operates draining the battery. So the battery on my car would drain after only around a day or two if the car hadnt been driven. Running a radio with the engine off in your car can theoretically drain your battery even if it is unlikely for most modern cars.
