107 Series Steering Wheel Removal
and Odometer Repairs
If your 107 has lost the odometer/trip odometer function, the likely cause is faulty/damaged gears in the odometer, housed in the Instrument cluster. The original MB gears were a urethane-like material that degrades and crumbles over time. This is exacerbated by the lubrication that is apparent on the gears, whether from the factory, or added later by a well-meaning mechanic.
The gears will loose teeth, and stop turning, which means the meters quit accumulating mileage [see photos]. In most cases I have read, the stepper motor keeps working, just not turning the meter gears. Replacement gears are available, and the process to repair the odometer itself is fairly straightforward.. Getting to the bugger; however, can be quite involved.
The subject of this page is confined to those odometers that are electrical/electronic. Mechanical variants do exist, and repairs are well documented on "the web". Specifically, this page chronicles the repairs I made to my 107.048, otherwise known as a 560SL. As this repair is also well documented, I borrowed some pictures from fellow Benzworld members, Nobby and Len Sokoloff, in lieu of taking my own. While Nobby's car is not a 560Sl, the illustrations are appropriate. His and Len's photos are used with annotation and permission here, with my thanks.
In order to get to the root of the problem, the instrument cluster must be removed from the nacelle (dash). The instrument cluster is held in place in the dash by Friction between a rubber collar and the dash and instrument cluster. MB (and others) make special tools to pull the cluster, although one can make the same tool from thin welding rod, coathanger, or other stiff wire [see photo]. The tool functions as a hook, and is inserted in between the cluster and dash pad, rotated, and engages the back side of the cluster. The cluster is then wiggled straight out of the dash while pulling on the wire tools. I was able to remove mine without the tools, by simply grasping the frame of the cluster, and gently wiggling and pulling forward. Had the friction fit been a little greater, I would have likely damaged the plastic frame, therefore, I do not recommend a repeat performance.
Here's where the fun begins. To get the cluster out, one must remove the steering wheel from the car. The procedure is relatively straight forward: remove the airbag, remove the countersunk allen screw from the center of the steering wheel, and remove the wheel. What befalls many that attempt this procedure is difficulty in removing the allen screw. When originally installed, permanent (red) threadlocker is applied and the screw is torqued to approximately 60 foot lbs. Several have reported being able to man-handle the screw out by brute force with a LONG handled breaker bar or similar, but others reported success with using an impact wrench. The risk is the head of the allen screw will strip, leaving you with the situation I faced on my rig.
Once the steering wheel is removed, and the cluster is out, the repairs to the odometer are fairly easy: remove the old gears, and replace with the new. Assemble, and go for a test drive!
Before beginning, assemble your tools [arsenal], and remove the ground cable on your battery. For those who still have functional alarm systems, be sure the alarm is not armed (doors are not locked), and the radio is turned off. This should prevent the radio from becoming "locked out". While I have removed my battery cables numerous times without these precautions, my alarm module has long since been removed. I have not had a radio lock-out issue with removing the battery, but others have reported such. For airbag equipped cars, remove the 10-pin plug on the airbag module under the carpet in the passenger floorboard, and wait at least 30 minutes before removing the airbag. Author's note: I did not remove the 10-pin connector, and the airbag did not explode.
Handle the airbag with care, and take measures necessary to protect yourself when handling/removing it. The gas-generating charge is quite powerful, and an unintended discharge could cause severe injury.
Steering Wheel Removal
To remove the steering wheel, one must gain access to the mounting screw in the center of the hub of the steering wheel. For the later model 560SL, the airbag must be removed to accomplish this (for earlier models without the airbag, this is accomplished by either removing the steering wheel center pad in its entirety, or removing only the MB 3-pointed star emblem in the center of the wheel). On the backside of the steering wheel from the drivers position, there are two torx screws that, when loosened, will allow the removal of the airbag. It is not necessary to remove the screws completely, but loosen until the airbag is free to lift away from the steering wheel. Once the airbag is released, a small red plug will need to be pulled straight out to completely remove the airbag [see photos]. After removing the airbag, take it and place it somewhere safe, and place it with the back side (metal side) down for safety if it were to somehow spontaneously activate.
Once you have access to the allen screw (or nut, on older rigs), remove the screw with a 10mm allen socket, and long breaker bar. DO NOT RELY ON THE STEERING WHEEL LOCK to apply counter-hold to the steering wheel. This will likely damage the locking pin of your ignition. Instead, use a 2x4 or similar to scotch the wheel against turning. Be sure to pad the end of the 2x4 to prevent damage to the steering wheel spoke(s), and turn your key to the unlock position of the ignition. You may try and wrench the screw out at this time, or even use an impact; however, I recommend you heat the screw to melt the threadlocker before ever applying torque to the screw. I wrapped wet paper towels in tinfoil, and placed them in the steering wheel cavity, to protect the airbag and horn wiring, and applied heat with a Bernzomatic pencil torch (Lowes, approx. $25USD). After heating sufficiently, apply torque counter-clockwise, and remove the screw. Be prepared to handle a hot screw, so as not to get burned or drop it, thereby permanently embossing its profile in your lap. If the screw still objects to removal, reheat, and try again.
If you should fail in removing the screw, and succeed in stripping out the screw head, it is not the end of the world. I tried to remove mine with a ½" electric impact wrench without heat, and promptly stripped out the head (even though I had purchased a band new Craftsman allen socket, and insured it was fully seated and tight in the screw by tapping it with a hammer to fully seat it into the screw). I then took a 3/8 drill bit, some WD40, and patience, and drilled a hole in the dead center of the screw, approximately 1" deep. After heating the screw, I then gently tapped a Kobalt ease-out into the drilled hole, and extracted the screw using an 18" crescent wrench on the ease-out. The screw still protested; however, the heated threadlocker was no match for the crescent wrench and my dogged persistence.
If you have to drill the screw, be sure to drill dead center of the screw. If you drill at an angle, you risk running out of the screw and damaging the threads of your steering shaft. I used a try-square to reference during the drilling process, and I removed shavings with a magnetic screwdriver several times to inspect my progress. Also, I recommend you obtain a replacement screw from MB ahead of time, if you do end up drilling yours. I did not, and decided to modify my "damaged" screw, effectively turning it into a bolt. I welded a ¾" nut on to the allen screw, allowing the use of a ¾ socket to tighten/remove, instead of the 10mm allen wrench [see photos]. Author's note: I did not reapply threadlocker when I reinstalled my steering wheel. Others have reported same without negative effects.
Once the screw is out, don't be surprised at how easily the wheel lifts away from the shaft. Instead, mark the steering wheel with a permanent marker to reference its location on the shaft before removing. The shaft will have a reference mark engraved on the end. Your mark will insure you install the wheel correctly so your turn signal cancel feature will still function as designed.
Now, go grab another beer (or favorite beverage) and relax. The hard part is over!
Assembly is basically the reverse of the process [see photos]. Insure your steering wheel is indexed according to your marks and the mark on the steering shaft, or your turn signal cancel function will be out of calibration with the steering wheel spokes.
Another recommended item is to polish the contacts on the back side of the steering wheel, and the contacts on the steering column [see photos]. The two contacts in the column in the upper half of the circle are for the horn, and the 4 in the lower half are for the airbags. Also, polish the contact rings on the back side of the steering wheel. This may correct the occasional flickering of the SRS light on the dash, if the contacts are dirty and have been loosing contact intermittently
Pulling the Instrument Cluster
As mentioned in the introduction, this is surprisingly easy to do. The cluster is held in only by friction, and I removed mine by grasping the plastic gauge frame on either side of the speedo and tach, and gently wiggled and pulled the cluster free of the dash. Had the cluster protested a bit more, I would not have been able to extract it this way, and either the MB tools or homemade tools would have been needed [see photos]. Use your best judgement on this one.
Once pulled out a bit, you will need to unplug the central connector, a few other electric connectors, the vacuum line to the economy gauge, and a few light bulbs/sockets. Be sure to orient yourself where everything goes. The bulbs/sockets that need to be pulled illuminate the information lights at the bottom of the cluster, and are likely numbered. The central connector is "keyed" so it can only be plugged up in one orientation, as are the other plugs. With the cluster out, you can now see two of the four vacuum pods that control the fresh air/re-circulated air for the Climate Control System. If you planned ahead, you can now easily rebuild these while you're in here. Also, you can inspect part of the windshield wiper mechanism, and the Defrost vacuum pod as well. You can even see the center vent pod arm, as it protrudes from the inside of the heater box to the vent flap in the center vents.
Assembly is the reverse, with one noted exception [see photo]. It has been written in numerous fora, that grounding issues plague 107 instrument clusters, and is manifest by flickering lights, and erratic gauge function. Take the time to install a separate ground, incorporating a plug to facilitate removal. The pictures presented in this webpage, will illustrate one way of doing this, but basically, install a lug underneath one of the instrument cluster bolts, and another to a good ground inside the dash. While this is not necessary, it is highly recommended.
Odometer repairs are well documented on numerous sites on the web, and instructions are also available from the replacement gear provider. Rather than repeat the complete step-by-step instructions here, I'll only provide an overview and any specific relative issues I faced with my repairs. Links to more complete instructions will be provided in the resources section at the end of this document.
The speedometer will have to be removed from the instrument cluster, to access the odometer [see photos]. Four small bolts around the speedometer will have to be removed, along with the two phillips screws holding in a set of warning lights (underneath the speedometer gauge), and the dash light illuminating rheostat will also have to be removed. Once all the screws are out, the speedometer is carefully extracted from the housing. Be advised, your speedometer needle and gauge face is now vulnerable to damage, so be careful. Once the speedo is out, remove the 4 bolts holding the white housing onto the speedo, and carefully remove it. Watch out for the 4 insulators on back of the circuit board, that they do not become lost, or misplaced. You should be able to see the odometer gears now, underneath a clear plastic cover. Note the damaged gears, and orient yourself with the relative placement of the gearsets. You will not be replacing all 5, but only three. Don't skimp. Replace all three, even though one or more of your existing gears may look good. I promise you they are fragile at this juncture of their lifespan. Remove the gear cover by removing two small screws, to gain access to the gears. The axle in each gearset may stick a bit in one or more of the gears, and must be re-used with the new gears.
Changing the pinion gear requires a bit of force, so be advised. Removing the old one is accomplished by "pinching" the old gear's brass sleeve with diagonal cutters, so as to expand its diameter. Done properly, it will slide off without using any prying force. Remember, you are working with the shaft of a small electric motor, so perform cautiously. When pressing the new pinion gear onto the shaft, sit the motor on top of something (pill bottle, etc) to help support the motor and housing while you use your fingers to press on the new gear. It will be a bit tough, but will slide on without the use of any tools. Be sure to spin the gears as you go, to insure they turn freely. No lubrication is necessary; however, there have been reports the new, hard plastic gears may be noisy. I used a small tad of petroleum jelly to dampen any noise, and they are quiet.
Assemble the gear casing, and the speedo back into the cluster. Voila! Before assembly, you may want to repaint your gauge needles on the gauges in your cluster. Documentation is available online if you wish. I encourage you to read up ahead of time, before attempting, and to afford an opportunity to plan accordingly, what tasks you hope to complete.
This was one of the more satisfying repairs I have performed on my 107. Excepting the difficulty of removing the steering wheel, it ranks as one of the more easy to perform as well. If difficulty in removing the wheel were not encountered, I'd give this a 3 on a scale of 1 to 10. Even with the drilling and screw extraction I had to do, I'd still rank it only as high as a 6, and only this high because of the drilling of the screw.
Good luck with your repairs, and share your efforts!
More information is available from the excellent 107 fora, residing at Benzworld.org, Peachparts.com, and of course, the MB service manuals, either CD or printed form. Also see the following specific threads:
Click Here! for Nobby's excellent tutorial.
Click Here! for the Encyclopaedia Germanica v 107.
Click Here! for the Author's experiences.
Click Here! for the source of replacement gears and instructions.
http://northernresource.com/mercedes/107.htm for an excellent resource page devoted to the venerable 107.