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Wiring Diagram

This component is part of Electrical Systems.


The appropriate wiring diagram for the 230SL, 250SL or 280SL is included in the Owner Manual. During the years the electrical system of the car went through a number of changes. Especially the US mandated anti-pollution measures are badly documented.

The Pagoda SL Group has published color coded diagrams for its members, courtesy of and copyright of Joachim Ahlert. These are accessible for Full Members here: Color Wiring Diagrams.

These comprise three diagrams:

  • Wiring Diagram for the early 230SL, May 1963
  • Wiring Diagram for the 230 SL, January 1966
  • Wiring Diagram for the 280 SL, August 1970

As a courtesy we provide a high quality grayscale version of the 280 SL wiring diagram, and a copy of a 280SL US version wiring diagram, showing additional features such as the transistorised ignition and emissions control relays.

Note: The description "Idle Increase Solenoid" for item 51 on "280SL (US Version) Wiring Diagram" is incorrect. The idle increase soleniod is uni-directional (extended when energized, spring return), whereas the solenoid on the schematic is bi-directional. What is shown appears to be the transmission solenoid which is three position with two coils, extended, mid positon, and retracted. The wiring indicates extended positon when the "venturi control switch" is closed, and retracted position when the "kick down switch" is closed, which is the function of the transmission solenoid. The "Idle Solenoid" does not appear on this schematic, nor do the forward and reverse auto-transmission pressure switches.

An exceedingly useful document is enclosed as a download in the Connectors section. It lists all connectors, pinouts, and colours of the main wiring circuit. If one of your connectors has broken and you need to hook it up again, this document is essential.

Colors of the Wires

The following official German Mercedes-Benz abbreviations of the colors for the wires are used:


Example: 1,5 sw/gn/rs means: 1,5 mm2 cable diameter, black cable with green and pink marking lines.


1Lighting unit, right
2Lighting unit, left
2.aHigh beam
2.bLow beam
2.cDirection signal light
2.dParking light
2.eFog light
2.fClearance light
3Glove compartment and reading light
4Switch for glove compartment light
5Heater blower switch
6Electric clock
7Entrance light and switch
8Speedometer light
9Revolution counter light
10Instrument cluster
10.aBlinker control light, left
10.bBlinker control light, right
10.cFuel reserve warning
10.dFuel level indicator
10.eInstrument cluster light
10.fRegulating resistor for illumination
10.gCharging control light
10.hHigh beam control light
11Loud dual tone horns
12Heater blower motor
13Illumination, heating control
14Door contact switch, right
15Door contact switch, left
16Windshield wiper? motor
17Relay for wiper motor
18Direction signal transmitter
19Relay for Electromagnetic Starting Valve (on early 230 SL)
19Luggage compartment lamp with switch (on a 280SL)
20Time switch (on 230 SL)
20Relay for automatic starting aid (on 280 SL)
21Relay for automatic starting aid (on 230 SL)
21Relay for Mixture Control (on 280 SL)
22Windshield washer pump
23Brake light switch
24Back-up light switch
25Cigarette lighter
26Signal ring
29Steering column switch
29.aBlinker switch
29.bHeadlight flash switch
29.cWindshield washer switch
29.dWindshield wiper switch
29.eSwitch for wiper speed
29.fPlug connection for steering column switch
30Series resistance
31Electromagnetic starter valve
32Thermo time switch
33Magnet for mixture control
34Brake fluid control switch
35Foot dimmer switch
36Rotary light switch
37Ignition starter switch
38Spark plugs
39Ignition coil
42Voltage regulator
44Fuel feed pump
45Transmitter for fuel gauge
46Plug connection tail light leads
48Tail light, right
48.fIdentification light, right
49Tail light, left
49.aDirection signal light
49.bTail light
49.cBack-up light
49.dClearance light
49.eBrake light
49.fIdentification light, left
50Becker radio
51Luggage compartment lamp with switch (on a late 230SL)

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