Date registered: Aug 2006
Vehicle: 2002 ML320, 2003 A160
Location: Brisbane, Australia
Mentioned: 2 Post(s)
Quoted: 484 Post(s)
That still doesn't explain why you want to know.
Having read the document, you understand that circuit 30 is hot at all times. When the car is switched off, there must still be power to operate the clock, remote control receiver, and alarm system - these are all connected to circuit 30.
Circuit 30g is switched by a relay. In modern MBs, some devices that remain on are automatically switched off after 6 hours or if the battery voltage drops below 11.8 V. This protects the battery from drainage. Systems on circuit 30g include seat controls, SRS components, sound system, and trailer hitch.