1988-93 Mercedes 300 Series Security Information
Constant 12V+	Red	Ignition Switch Harness or Driver's Kick Panel
Starter	Purple/White or Purple	above Pedal
Ignition	Pink/Red or Red/Black	Ignition Switch Harness above Accelerator
Ignition 2	Pink/Yellow	Ignition Switch Harness, Accessory 2
Accessory	Pink/Green	Ignition Switch Harness
Tach	Black	Or Gray/Yellow (-) At Coil left inner fender
Brake Switch	Black/Red	Brake Switch
Trunk Pin	Black/Yellow (-)	OEM Alarm Module Passenger's FootWall
Parking Lights	Gray/White L	And Gray R at Light Switch
Head Lamp	White/Yellow	Light Switch
Hood Pin	Brown/Red (-)	OEM Alarm Module Passenger's FootWall
Factory Disarm	Green/Yellow (-)	OEM Alarm or Driver's Kick Panel
Door Trigger	Brown/ (-)F	,Brown/ (-)R at OEM Alarm right FootWall
Door Lock	Green or Blue	Driver's Kick or Pump under Rear Seat
Door Unlock	Green or Blue	Vacuum Door Lock System
Horn Wire	Black/Pink (+)	Steering Column
Windows Up	LF=Green, RF= Black/White
Windows Down	LF=Black/Pink, RF= Black

Vacuum Type Door Locks

Found mostly on Mercedes Benz vehicles, the movement of the door lock actuators is controlled by a central vacuum pump. The switch changes polarity on a single wire that may rest at power or ground depending on the state of the door locks. You can duplicate this with at least a 2 second pulse. If the alarm or keyless entry you are installing does not have a 2 second or longer duration option for the door lock outputs, do not use this diagram (it will not work unless you incorporate a timer into this circuit).