A plastic shaft within the scroller knob unit snaps causing the scroll function to no longer work on the screen.
It is a common fault on these vehicles for the comand controller knob to stop functioning correctly. A poor-quality plastic shaft within the controller knob unit snaps. This causes the common symptom of the scroller rotating as normal but for there to be no reaction on the screen. If all other functions are working except the scroll this indicates this shaft has deteriorated and snapped, this is an extremely common fault. Mercedes Benz fix is to replace the complete knob and button unit, this is extremely expensive and would only fail again.
Symptoms of the fault
Knob rotating but no response on the monitor. Knob works up-down-left-right but no rotation. When the wheel is turned, no reaction on the screen will be shown. All other functions such as confirming and tilting the controller are given.
Vehicles affected and compatibility
C-Class W204, C204, S204. CLA-Class C117, X117. E-Class W212, S212, A207, C207. CLS-Class S218, X218. GLK-Class X204, X218. SLK-Class R172.
Associated part numbers:
A2048700779,A2048700879, A2048702058, A2048702158, A2048704558, A2048704658, A2048707458, A2048707558, A2128702851, A2128702951, A1728701258, A2048700179, A2128701351, A2128701451, A2128701551, A2128702751, A2048707658, A2048707758, A2048708851, A2048708951, A2048700579, A2048700679, A2048701258, A2048709558, A2048709758, A2048709958, A212870275, A2048700779, A2048702058, A2048700779, A2048702058.
This information is for guidance only, please inspect your comand knob unit to ensure compatibility.
Restore full function with our replacement metal shaft.
Our part allows you to replace just the shaft within the knob unit which fails, without having to replace the complete unit at vast expense which would just fail again. Our shaft is CNC machined from billet aluminium then anodised. Beware of 3d printed, plastic and cast metal parts which could fail again. Our part will last the life of the vehicle. Using our part replace just the component that fails with an improved design part and restore full function permanently.
You will receive
1X Replacement CNC billet anodised aluminium rotary shaft.
Please bare in mind that these units can differ slightly from car to car and the our new shaft will fit a variety of part numbers so these instructions should be used as a guide to the basic procedure for installation.
You will require various hand tools for this repair and again these may differ from unit to unit but for this unit we used:
A large flat head screw driver.
A small flat head screwdriver.
A T7 torx head screw driver.
A T10 torx head screw driver.
You may also need plastic pry tools, depending on how tough it is to separate the unit.
Step 1: Remove Outer Scroll Ring
For this we used our large flat head screwdriver but you could also use a plastic pry tool.
Gently lever the outer ring upwards, working your way around the base, small bits at a time until the ring is loose enough to remove with your fingers.
Be careful not to damage the unit or the outer ring.
Step 2: Remove the Top Ring and Top Button Cover
Using the small flat headed screwdriver or a pick tool, gently lever the top ring away from the base.
Once this is away, you can gently lever the top button cover away using either the flat head screwdriver or a small plastic pry tool.
Step 3: Remove the Scrolling Dial
Use a T7 torx head screwdriver to remove the central screw (may vary by model). You will need to apply pressure downwards on the dial and then unscrew for it to come away.
Step 4: Remove the Screws That Hold the Unit Together
Flip the unit over and you will see the screws (again, this can differ from unit to unit, ours had 10) that hold the two halves of the unit together.
We used a T10 torx screwdriver to remove them. Once removed store safely.
Step 5: Separate the Two Halves
Now the screws are removed you can separate the two halves of the unit. Ours came apart quite easily but you may need a plastic pry tool or flat head screwdriver to separate them if it proves tough.
You will now be able to see the insides of the unit and its time to take extra care not to damage the components or the circuit board as this could lead to a malfunctioning unit even with our new shaft fitted.
Step 6: Remove the Shaft Components
Carefully lift away the 4 components that are located around the shaft cover.
Important! Place these in the order they came off as they will need to be placed back in the correct order for the unit to work properly.
Step 7: Remove Small Plastic Levers
You will now need to remove the 4 small levers from the 4 plastic housings.
Carefully use a small flat head screwdriver to pry the levers out being careful not to damage anything. Store these safely.
Step 8: Remove the Lever Housings
Using a small flat head screwdriver, gently pry the tab outwards and then pull the housing upwards to remove it from the circuit board. Do this for all 4 housings.
Be careful not to break the tabs by levering them too far.
Step 9: Remove the Circuit Board
Firstly, remove the wiring from its retaining plastic channel on the unit housing.
Once this is free, very carefully lift the circuit board away from the rest of the unit up over the shaft cover.
Store this safely.
Step 10: Remove the Shaft Cover
You can now remove the plastic cover that protects the control shaft.
This will just lift away and will reveal the broken shaft which has been causing the issues with functionality.
Step 11: Check the Units Parts
Make sure you have safely stored or placed all the parts you have removed.
Step 12: Fit Our Aluminium Shaft
It is now time to fit our aluminium shaft and rebuild the unit.
The shaft just needs to be placed on the bottom locating square and then the plastic shaft cover can be placed over the top of it to hold it upright.
Step 13: Refit Circuit Board
Now refit the circuit board making sure it is the correct way up.
Make sure to locate the wire back in the retaining channel also.
Step 14: Reinstall Levers
Its usually best to reconstruct the lever into the lever housing BEFORE installing them back onto the circuit board.
These just clip into place and make sure the "leg" of the lever faces down and outwards.
Once the 4 levers are back in their housings, the housings can be push fitted back onto the circuit board.
Make sure the lever legs are facing inwards towards the shaft.
Step 15: Reinstall Components
Reinstall the components in the correct order (the reverse order of how they were taken off).
See pictures for the order of placement if unsure.
Step 16: Reconnect Two Halves of Unit
You can now place the two halves of the control unit back together. Sit bottom half on your workbench and place the top half down onto it to make sure nothing falls out.
Once joined, hold the unit together and turn it over onto its front to refit the screws with the T10 torx screwdriver.
Step 17: Refit the Scroll Dial
Place the dial back onto the unit. Rotate it until it locates correctly.
Refit the screw using the (in our case) T7 torx screwdriver. Do not over tighten this. You will need to apply pressure downwards onto the dial whilst screwing in the screw.
Step 18: Refit the Top Cover, Top Ring and Outer Ring
Place the top button cover on the dial centrally.
The top ring has locating lugs on it that should correspond with locating holes on the top edge of the dial. Place these lugs in the holes and gently press down making sure the the ring is secure around the top cover.
Lastly, refit the outer scroll ring. There are 3 locating strips on the inside of the scroll ring which will slot down into 3 locating grooves on the outside edge of the scroll dial.
Push down until this clicks and it should now be securely in place.
That concludes the replacement of the command control unit shaft.
We advise to test the unit by connecting it to the power in the car before fully reinstalling the unit in the vehicle.
This completes the repair. If you need any further guidance on this install or would like to purchase the parts shown please call us on +44 01843 446643 or email us at firstname.lastname@example.org.
Please also check out our instruction guide on YouTube.
Installation is carried out at installers risk, if unsure please contact us or a professional, X8R Ltd cannot be held responsible for any adverse result of installing this product or any injuries caused by install, if in doubt ask a professional. All images and texts are copyright X8R Ltd 2019