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Clock Speedometer and Bulb Replacement
 
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Pelican Technical Article:

Clock Speedometer and Bulb Replacement

Steve Vernon

Time:

1 hour1 hr

Tab:

$4 to $400

Talent:

**

Tools:

Philips head screwdriver driver

Applicable Models:

Mercedes-Benz W123 (1977-85)

Parts Required:

Instrument parts as needed

Hot Tip:

Do pull hard on the cluster

Performance Gain:

Working instruments

Complementary Modification:

Check all your bulbs

Unlike modern cars where the instrument cluster is one sealed module, the instrument cluster on the W123 can be replaced separately. When something fails you do not need to replace the entire cluster, only the bad components. To do this you will first need to remove the cluster. There are a couple of things you need to be aware of; it is a tight fit behind the cluster so do not try and yank the cluster forward when removing it, you will need to reach your hand behind to release a few things to get some working room, also if your cluster is old and you are using the cluster removal tool make sure to make sure it is seated on the cluster and not the front plastic shield as you can pull this straight off the cluster if you do.

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

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.

Begin by removing the cluster housing from the dash; please see our article on instrument cluster removal for additional assistance.

Besides the bulbs, the three main components you can change are the: clock (red arrow), the speedometer (yellow arrow) and the gauge dimmer potentiometer (blue arrow).
Figure 1

Besides the bulbs, the three main components you can change are the: clock (red arrow), the speedometer (yellow arrow) and the gauge dimmer potentiometer (blue arrow).

To replace your instrument gauge bulbs (red arrows) simply grab the base of the bulb and turn 45 degrees, this will release the bulb from the board.
Figure 2

To replace your instrument gauge bulbs (red arrows) simply grab the base of the bulb and turn 45 degrees, this will release the bulb from the board.

The base and the bulb are one piece and will be replaced together; the bulb does not pull out from the base.
Figure 3

The base and the bulb are one piece and will be replaced together; the bulb does not pull out from the base. Installation is the reverse of removal.

You replace the potentiometer by using a Philips head screwdriver to remove the single screw that holds it in place.
Figure 4

You replace the potentiometer by using a Philips head screwdriver to remove the single screw that holds it in place.

You can now pull the unit form the board; there is a shaft that will need to pass through the mechanism when reinstalling it.
Figure 5

You can now pull the unit form the board; there is a shaft that will need to pass through the mechanism when reinstalling it.

To replace the clock use a Philips head screw driver and remove the four screws that hold it in place (red arrows).
Figure 6

To replace the clock use a Philips head screw driver and remove the four screws that hold it in place (red arrows).

With the screws removed you can carefully lift it out from the housing.
Figure 7

With the screws removed you can carefully lift it out from the housing.

To replace the speedometer you will first need to remove both the clock and potentiometer (yellow arrow) and then remove the two remaining Philips head screws (red arrows).
Figure 8

To replace the speedometer you will first need to remove both the clock and potentiometer (yellow arrow) and then remove the two remaining Philips head screws (red arrows).

There will be an arm attached to the mechanism (red arrow) when you remove it, so do not just pull it out.
Figure 9

There will be an arm attached to the mechanism (red arrow) when you remove it, so do not just pull it out. Take your time and move the upper wires out of the way.

Once everything is clear you can remove and replace the speedometer.
Figure 10

Once everything is clear you can remove and replace the speedometer. Remember it is a crime to not state the true mileage of a vehicle. Make sure you check the regulations in your area before installing your new speedometer. Installation is the reverse of removal.

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Page last updated: Fri 12/9/2016 03:02:33 AM