What you are describing is called a "Parasitic Drain"
In automotive terms, a parasitic drain is an electrical load that draws current from the
battery when the ignition is turned off. Some devices, such as the PCM and the radio memory are intended to draw a very small amount continuously. These draws are measured in milliamps (mA).
An abnormal parasitic drain could be something like a glovebox lamp, lighted sunshade mirror, aftermarket accessory, or luggage compartment light that remains on but undetected. Or an electronic component may malfunction and cause a parasitic drain that is larger than normal specification.
The recommendation for maximum parasitic drain is around 30 mA (0.030 amp). A typical drain today actually falls into the 7-12 mA range, even though some vehicles do approach the maximum.
Unfortunately, many mechanics do not know how to properly test for and/or track down a parasitic drain. You need to find a shop that has a technician that is familiar with this type of problem. The best way is to ask them specificly if they know how to diagnose a parasitic drain. If they hesitate, or act like they don't know what you are talking about, move on to the next shop.
×