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Ignition Switch

The ignition switch and ignition key are used to power the car and allow it to start. It is a major component of the Ignition System.

Definition

Ignition key


230 SL Ignition Key


The ignition key for a 230SL is a one-sided key, whereas the 280SL ignition key is a two-sided key. They are not interchangeable!

There are two versions of the steering lock mechanism for a 280SL:

The OEM for ignition locks and keys was the Neiman Company. Reproduction keys were made by several different companies. Equivalent part numbers for these are as follows:

  • OEM: Neiman Code Series D11111 - D55555
  • Ilco: MB59
  • Dominion: H63N
  • Curtis: MB17
  • Silca: NE8
  • Taylor: M68

Apparently those made by Taylor are 0.010 inch thinner than other varieties.

Ignition switch.

This is the ignition switch in a late 230SL:


Ignition Switch Mechanism


Function

Describe, in general terms the function of this component.

Maintenance

Stuck Ignition key

Sometimes there is a problem with turning the key in the ignition. When trying to start the car, it stuck between position 1 and 2. The car was off and the ACC power could just barely be switched on, but the car could not be started. Also, the key could not be removed.

Think of the ignition switch as having three major components;

  • the electrical switching unit (simply attached to the back of the assembly with three screws, this does all the electrical work)
  • the lock assembly wich is the key and tumbler unit which is removable from the front
  • the steering lock assembly which inserts a pin in the steering column when the key is removed. This requires major disassembly (dash gauges out etc) to remove.

Try a dry lubricant first (graphite lubricant) and as last resort a liquid (WD-40 or Wurth Lock Lubricant Part # 0893-051U). Also before you give up clamp down on the key with vice-grips and try to yank it out. The tumbler assembly is removable by turning the key to the first position and removing the inner chrome bezel by pulling outward. Now the trick is to turn the key back off and remove the key to finish removal of this inner chrome bezel. A "e" clip beneath this chrome part holds the tumbler assembly in place.

Car does not start

On a 230SL '65. When the key is turned everything powers up, yet when it is turned to start, it often doesn't. Sometimes it takes several tries. It might be a short at the key switch.

If you have an automatic transmission it as a safety switch in the circuit that might prevent it from starting. Verify that also before dismantling the ignition switch.

Diagnostic procedure:

The problem can be:

  • either a bad starter contact ring in the ignition switch OR
  • possible bad starter/brushes/solenoid (or wiring in between) OR
  • the key may be improperly cut

Take a test wire and jumper from terminal "G" at the time thermo switch (this will be the short terminal) to Battery B+, the starter should turn (make sure you are in "N" for this jumper test). Do it a few times, and if the starter cranks every time, it is working correctly... and consequently the start/ignition switch is bad.

If the starter does not turn every time the test wire connection is made, there is a problem at the starter.

There have also been instances where the key itself was the problem. If you are using a non-MB ignition key you should try an original key (hopefully you have a copy, but if not you should be able to obtain one through Mercedes Benz). Modern, non-MB blanks may be slightly misshaped and not make proper contact to engage the starter; the fuel pump, etc. will run (as described above) but the starter solenoid will not energize or will do so only on occasion. If you've eliminated the key and the starter as the problem it may be time to look at the ignition switch itself.

In a 230SL lock there is nothing in the key tumblers or locking bolt that will prevent the key from turning from the run to start position. The stop is inside the electrical switch assembly. With the switch removed from the lock the key will turn past the point where the starter would engage. The ignition switch contains a mechanical lock out that prevents the starter from engaging a second time unless the ignition is turned to the off position. It is usually a failure of this lock out that prevents the switch from engaging the starter.

The tell tale sign that the key tumbler is about to fail is a crack becomes visible below the key, on the side of the tumbler where the flat side of the key goes into the slot.

On rare occasions the ignition switch can go bad. The steering lock/ ignition switch assembly has a separate Ignition switch unit on the back of the assembly. It is held on by three small slotted screws. It will remove easily however getting to it is difficult since the instruments need to be removed first! Make sure every thing else is ok before taking the plunge.

Ignition key falls out of switch

The key won't stay in position to keep the engine running! The car starts and runs just fine... but it's gotten to the point where the key needs to be held in position or it springs to the off position.

There is an ignition switch unit at the rear of the ignition/steering lock assembly. This unit can be replaced without removing the whole ignition assembly but unfortunately the speedometer may have to be removed to access it. Three small screws hold it to the back of the assembly.

There are at least two versions of the ignition switch depending on the year of the W113. The parts book shows two versions early # 000 462 0693 and late # 000 462 17 93. Parts suppliers should be able to refer to the vin # of the car for the correct switch. Sedans of the era used the same parts.

Removing the ignition switch

When the ignition key is jiggled while the car is running, it will stop. Sometimes the bolt mechanism, when worn, won't fully turn the electrical contacts when the key is turned. The switch itself or the electrical contacts may go bad too.

To replace the entire ignition switch assembly which includes the lock mechanism for the steering, you need to remove the instrument cluster gauges, unbolt the steering column. When you've removed the steering column, the steering lock shaft is attached to the steering column and the ignition key assembly by a 'C' clamp with a 6mm bolt. This is visible when the instruments and steering column are out of the way.

Then you remove the three screws that attach the switch, reconnect the wires to the new switch (make sure you keep track of the wires as you do this), then screw in the new switch. None of this is complex, nor does it require special equipment. It does require flexible hands and fingers....lots of patience. Be sure that the plastic/metal connection of the part is solid and secure. You may want to glue the two pieces because they can slightly come apart shortly after replacement and then you will need to go through the entire procedure again. If you have a good mechanic and value your time, you might consider letting him do it.

The whole procedure will take a day.


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