Difficulty

Moderate

Steps

12

Time Required

                          20 minutes

Sections

1

  • Instrument Cluster
  • 12 steps

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Introduction

What you need

Step 1

              Instrument Cluster
  • Begin by disconnecting your battery, pulling off the negative (-) ground cable.
  • This is required for this process! There is a constant 12v supply of power to your car’s clock, even when the key is off. If you attempt to pull the cluster out with the battery connected you will burn up part of your cluster’s circuit board, or worse yet hurt yourself.

Begin by disconnecting your battery, pulling off the negative (-) ground cable.

This is required for this process! There is a constant 12v supply of power to your car’s clock, even when the key is off. If you attempt to pull the cluster out with the battery connected you will burn up part of your cluster’s circuit board, or worse yet hurt yourself.

1024

Step 2

  • Then remove the driver’s side kick panel. See the kick panel removal guide for help with this task.

Then remove the driver’s side kick panel. See the kick panel removal guide for help with this task.

Step 3

  • The cluster is held in by tension alone. There are no fasteners.
  • Reach up under the dash, feel your way past any wires and/or sound insulating material until you can touch the back of the cluster. Then push it firmly outwards towards the steering wheel.

The cluster is held in by tension alone. There are no fasteners.

Reach up under the dash, feel your way past any wires and/or sound insulating material until you can touch the back of the cluster. Then push it firmly outwards towards the steering wheel.

Step 4

  • Once the cluster starts to come out, you can pull it further out by the upper edge.

Once the cluster starts to come out, you can pull it further out by the upper edge.

Step 5

  • Pull the cluster out until you feel the tension of the speedometer cable.
  • Normally, there will be just barely enough room for you to get your hand behind the cluster. You will need to feel around the center of the cluster, behind and to the right of the center of the speedometer cable, for the connection for the speedometer cable.
  • The cable screws on to the back of the cluster with a knurled knob. It is to be loosened by hand. No tools will be necessary to unscrew this. Unscrew the cable until it is free of the cluster.
  • If your speedometer cable is especially taut behind the cluster, you may need to go back to step 2 and try to remove it by feel before pushing the cluster out by hand.

Pull the cluster out until you feel the tension of the speedometer cable.

Normally, there will be just barely enough room for you to get your hand behind the cluster. You will need to feel around the center of the cluster, behind and to the right of the center of the speedometer cable, for the connection for the speedometer cable.

The cable screws on to the back of the cluster with a knurled knob. It is to be loosened by hand. No tools will be necessary to unscrew this. Unscrew the cable until it is free of the cluster.

If your speedometer cable is especially taut behind the cluster, you may need to go back to step 2 and try to remove it by feel before pushing the cluster out by hand.

Step 6

  • With the speedometer cable disconnected you will be able to pull the cluster out further for more working room.
  • Starting on the right side, begin disconnecting the items that attach to it.
  • First, you will pull out any light bulbs that plug in to the right hand side of the cluster. On a diesel W123 this will include the glow plug bulb and seatbelt bulb. Then unplug the spade connector for the power supply to the clock.

With the speedometer cable disconnected you will be able to pull the cluster out further for more working room.

Starting on the right side, begin disconnecting the items that attach to it.

First, you will pull out any light bulbs that plug in to the right hand side of the cluster. On a diesel W123 this will include the glow plug bulb and seatbelt bulb. Then unplug the spade connector for the power supply to the clock.

Step 7

  • Next, unplug the two small plugs near the middle of the cluster.

Next, unplug the two small plugs near the middle of the cluster.

Step 8

  • Next, use a 10mm wrench to unscrew the oil line from the oil gauge.
  • Lastly, unplug the large round plug on the far left of the cluster, down and to the left of the oil gauge fitting.

Next, use a 10mm wrench to unscrew the oil line from the oil gauge.

Lastly, unplug the large round plug on the far left of the cluster, down and to the left of the oil gauge fitting.

Step 9

  • With everything disconnected you can now remove the cluster, carefully working it up and out past the steering wheel.

With everything disconnected you can now remove the cluster, carefully working it up and out past the steering wheel.

Step 10

  • With the cluster removed on this car, let’s take a second to identify some of the connections:
  • Speedometer cable
  • Oil line fitting
  • Small plugs for cluster accessories and lighting
  • Large primary plug
  • Not pictured are the wires and bulbs for the glow plug and seat belt light, and the spade plug for the clock. Keep track of which bulb went in which socket - the wires will be different colors. On this car the wire for the seat belt light was green and the glow plug bulb wire was blue.

With the cluster removed on this car, let’s take a second to identify some of the connections:

Speedometer cable

Oil line fitting

Small plugs for cluster accessories and lighting

Large primary plug

Not pictured are the wires and bulbs for the glow plug and seat belt light, and the spade plug for the clock. Keep track of which bulb went in which socket - the wires will be different colors. On this car the wire for the seat belt light was green and the glow plug bulb wire was blue.

Step 11

  • You can now take the cluster to your work bench to undertake whatever job you removed it for.
  • Let’s review the components, both front and back:
  • Oil pressure gauge, gas gauge, and engine temperature gauge
  • Speedometer, odometer and trip odometer
  • Tachometer and clock

You can now take the cluster to your work bench to undertake whatever job you removed it for.

Let’s review the components, both front and back:

Oil pressure gauge, gas gauge, and engine temperature gauge

Speedometer, odometer and trip odometer

Tachometer and clock

Step 12

  • And a bit more detail about the components on the back of the cluster:
  • Light bulb sockets (some are used, others are blanked out)
  • Speedometer cable connection
  • Rheostat (dimmer) control
  • Oil line connection
  • Clock spade connector (note +12v symbol, this is the constant 12v supply that can damage your cluster if battery is not disconnected)
  • Large primary cluster pins
  • Accessory plugs

And a bit more detail about the components on the back of the cluster:

Light bulb sockets (some are used, others are blanked out)

Speedometer cable connection

Rheostat (dimmer) control

Oil line connection

Clock spade connector (note +12v symbol, this is the constant 12v supply that can damage your cluster if battery is not disconnected)

Large primary cluster pins

Accessory plugs

To reassemble your device, follow these instructions in reverse order.

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Author

                    Nicolas Siemsen

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brandon - Jan 14, 2016

Reply

Any chance you can tell us what color of wires goes on each of the 15 pins from the large primary plug (Cluster pins) or even show a picture of where it all goes? Some of my wires got mixed up and it’s really hard to tell which wires goes to what pins…

brandon - Jan 15, 2016

FYI I have a 85’ CD300 if that helps. ;-)

Nicolas Siemsen - Feb 4, 2016

Hi, here is a link to a picture of the pin out diagram for the 15 pin plug behind the cluster.

http://www.benzworld.org/forums/attachme…

Jesmond Mifsud - Sep 28, 2016

Reply

Hi all, I am looking for Mercedes Benz W123 speedometer part no. 1235423601 0085425606

Any idea where I can find a store or supplier providing genuine new parts, thanks

fixitsteve - Apr 29, 2018

Reply

Does it matter what direction the accessory plug on the speedometer is plugged in? It seems to go on both ways and I’m not sure if I am installing it right!