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Ignition Switch and Assembly Replacement
 
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Pelican Technical Article:

Ignition Switch and Assembly Replacement

Steve Vernon

Time:

1 hour1 hr

Tab:

$40 to $575

Talent:

**

Tools:

10mm wrench, Mercedes tool 140598023300, flathead screwdriver, thin piece of sturdy metal

Applicable Models:

Mercedes-Benz W123 (1977-85)

Parts Required:

Switch or Assembly

Hot Tip:

Take your time

Performance Gain:

Working ignition

Complementary Modification:

Replace dash bulbs

Repeated use of the ignition assembly may cause it to fail over time. Fortunately it is a relatively easy repair job. There are two parts that make up the ignition switch assembly; the housing and the switch portion. If the electronic switch portion on the rear of the assembly goes bad you will unfortunately need to remove the assembly to replace it. You will be working under the dash so even though it may not be necessary it is a good idea to have a flashlight handy.

Over the years your car may have been serviced by multiple people including previous owners and this can lead to parts replaced with different size fasteners and hardware. The sizes of the nuts and bolts we give may be different from what you have so be prepared with different size sockets and wrenches. If something is different on your vehicle please let us know and share your info to help other users. If you have any questions or comments or even a different procedure you would like to share please leave it below and please leave your vehicle information.

Make sure that you disconnect the battery ground cable before you begin as you are going to be with the cars electronics.

NOTE: We have removed the steering wheel so we could get pictures of the wiring but you do not need to remove your wheel to remove the ignition tumbler.

Disconnect the negative battery cable (red arrow).
Figure 1

Disconnect the negative battery cable (red arrow). Make sure it cannot make accidental contact with the battery while working.

Remove the five Philips head screws holding the lower dash under panel in place and remove it from the car.
Figure 2

Remove the five Philips head screws holding the lower dash under panel in place and remove it from the car. Please see our article on under dash panel removal for additional assistance.

You will need Mercedes tool 140598023300 or a homemade equivalent to remove the instrument cluster; please see our article on instrument cluster removal for further help.
Figure 3

You will need Mercedes tool 140598023300 or a homemade equivalent to remove the instrument cluster; please see our article on instrument cluster removal for further help.

Remove the plastic or rubber surround (red arrow) by simply pulling it away; on some models you may need to bend the tabs back that hold the surround in place.
Figure 4

Remove the plastic or rubber surround (red arrow) by simply pulling it away; on some models you may need to bend the tabs back that hold the surround in place.

You are going to need a thin strong piece of metal that should be less than 1.
Figure 5

You are going to need a thin strong piece of metal that should be less than 1.25mm in diameter. It is a good idea and will make removing the tumbler much easier if you file the end down to a beveled edge.

Insert the key into the ignition and turn it to the accessory or first position (red arrow).
Figure 6

Insert the key into the ignition and turn it to the accessory or first position (red arrow). The opening in the tumbler will be just before the first position; this is where you want to insert your wire (yellow arrow).

Press the wire in until it releases the lock on the theft prevention tube that surrounds the tumbler (red arrow).
Figure 7

Press the wire in until it releases the lock on the theft prevention tube that surrounds the tumbler (red arrow). This can be tricky the first time you do it so take you time and you will get it. Sometime the black theft prevention tube will move forward when you release the lock other times you just have to try and turn the tube by hand to discover if you have released the lock.

Once it is unlocked turn it counter-clockwise until it comes off the ignition housing.
Figure 8

Once it is unlocked turn it counter-clockwise until it comes off the ignition housing.

You can now remove the anti-theft tube from the old tumbler as you are going to re-install the tumbler without the tube to remove the assembly.
Figure 9

You can now remove the anti-theft tube from the old tumbler as you are going to re-install the tumbler without the tube to remove the assembly.

Reach into the opening and wiggle and pull the electrical connector from the rear of the ignition assembly (red arrow).
Figure 10

Reach into the opening and wiggle and pull the electrical connector from the rear of the ignition assembly (red arrow).

Carefully label and remove the two vacuum lines (red arrow, if equipped) from the side of the assembly.
Figure 11

Carefully label and remove the two vacuum lines (red arrow, if equipped) from the side of the assembly.

Working from under the dash disconnect the electrical connection from the assembly (yellow arrow) and using a 10mm wrench loosens the clamping collar (red arrow) on the assembly.
Figure 12

Working from under the dash disconnect the electrical connection from the assembly (yellow arrow) and using a 10mm wrench loosens the clamping collar (red arrow) on the assembly.

Press down on the lockout tab and reinsert the tumble into the assembly (red arrow).
Figure 13

Press down on the lockout tab and reinsert the tumble into the assembly (red arrow). Turn the key to position one which is the same position you used to remove the tumbler.

Working under the dash press in the release tab on the assembly by the locking collar (red arrow).
Figure 14

Working under the dash press in the release tab on the assembly by the locking collar (red arrow). You can use a 3mm Allen or other suitable tool. Once the tab is pressed in turn the key back to the 0 position and remove the key. The tab can only be depressed when the ignition is in the 1 position.

Rotate the assembly upward until the tumbler clears the front of the dash and remove the assembly.
Figure 15

Rotate the assembly upward until the tumbler clears the front of the dash and remove the assembly.

With the assembly out from the dash and column you can better see the release tab you will be depressing (red arrow).
Figure 16

With the assembly out from the dash and column you can better see the release tab you will be depressing (red arrow).

To replace the switch remove the three flathead screws (red arrows).
Figure 17

To replace the switch remove the three flathead screws (red arrows).

You can now separate the switch from the assembly.
Figure 18

You can now separate the switch from the assembly. Installation is the reverse of removal. Make sure to install the assembly with the key in the number 1 position as this is the only position you can depress the locking tab, then turn the assembly until you hear the release tab lock into position, remove the key and then tighten the collar.


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