Hello, newbie here. Have a 1996 SL320 that normally behaves well but today there's a loud pinging alert sound that started after we'd been driving for 2-3 miles and continues whenever the key is at ignition stage 2, whether the engine is running or not. Recently the battery was completely flat after a week or two of non-use. This is not normally a problem, it usually holds its charge well. We jump started the car and noticed various features only worked as the battery gained a fuller charge: e.g. window single click full open / window drop & back up when opening or closing the door. Have looked for obvious things: i.e. opened & shut doors, boot, bonnet; removed the hard top, closed and re-opened the soft top, put the hard top back on again. No joy - as soon as the ignition key is turned to stage 2, the pinging alert goes again. Help please!!!