Execution order
1. Using the test lamp's needle contact, you can pierce the wire insulation and determine which wire has voltage.
2. Find the electrical diagram for each switch.
3. First, check whether voltage is supplied to the switch at all; in this case, you need to turn on the ignition or lighting several times.
4. Then it is checked whether there is conductivity in the switch in the corresponding position.
5. Using the ignition switch assembly as an example, it looks like this:
6. Remove the top and bottom steering column trim as described in the section on removing the lever switches earlier in this chapter.
7. Connect the test lamp connecting wire to ground.
8. Pierce the insulation of the wire being tested with the test tip.
9. Both terminals of the 30 thick red wire should always be under voltage from the battery.
10. Gray/yellow wire of terminal P in position "Ruhestellung" (rest) of the ignition switch is energized and is de-energized when it is turned.
11. Black/yellow wire terminal X (and also terminals 75) is energized only in the key position "Zundung ein" (ignition on).
12. The thin red wire to terminal 86s is live until the key is removed. This is where the radio is connected, as well as (for information) interior lighting switch-off delay relay and signal buzzer in the combination instrument.
13. The black wire of terminal 15 receives voltage in the key position "Zundung ein" (ignition on) and "Anlassen" (engine start).
14. The red/black wire from terminal 50 of the start signal to the starter is energized only in the "Anlassen" position (engine start)
15. Terminal 50b has the same function as terminal 50, it serves to pre-excite the generator already during the engine starting process.