What's stopping my 740ill from goin in to sleep ride in its computer on 1995 BMW 740iL

My boss bought a bmw 740ill n had to put a shut down switch to cut off all main power time the car cuz if it didn't have that switch you come to a dead battery the next day when you went to fire the car up anyone have any idea why it might not be goin in to sleep mode? This problem happens when the battery is connected to the car but when the battery is hooked up it'll keep a charge

Asked by for the 1995 BMW 740iL
1 answer
seek a good electrical shop to diag issue