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Date registered: Aug 2006
Vehicle: 02 ML320 06 ML500
Location: Bronx, New York
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What happens with any ignition lock cylinder is sometimes one of wafers/pins in the cylinder gets "hung up". Depending which pin it is determines whether you can partially turn the cylinder or not turn the cylinder at all. The only thing that will possibly make the lock work again is lubrication and a little shock therapy.
What you need is a 6-7 in. long wooden or plastic dowel, the diameter of which must be smaller than the diameter of the lock face and a spray can of Lock-Easehttp://www.acehardwareoutlet.com/(1berypmlmgmhuwvg32ab1d45)/ProductDetails.aspx?SKU=10716. When buying the Lock-Ease make sure that it has the red flexible straw taped to the can.
The first order of business is to bend the tip of the straw to a 45 degree angle, with the help of a hair dryer.
1. With the straw inserted in the spray nozzle, insert the straw into the keyslot with the 45 degree tip facing upwards until it reaches the back of the cylinder.
2. Press the nozzle and slowly pull the can and straw outwards until the full length of the keyway has been sprayed. Do this once more. Don't worry about the bottom part of the lock as the residual spray will lubricate it.
3. Wait about 15 mins.
4. Then insert the key in and out of the lock cyl. approx. ten times and then attempt to turn the cyl. in the normal fashion. Repeat the process 2-3 times if the cyl. does not turn.
5. If the above does not work, spray the inside with Lock-Ease, take the wooden or plastic dowel and hold the end of it 1/4 inch away from the face of the lock cyl. Then strike the dowel with a light hammer 2-3 times., each timeholding the dowel away from the face. Light taps with the hammer will not do the trick. Don't over do it, but believe me more force is necessary than light taps.
6. Then insert the key and attempt to turn the cyl. You might be successful on the first try or you might have to do this 10 times but the lock will eventually turn. Patience is necessary. My longest encounter with a Mercedes lock was 45 mins. Don't be afraid to strike the lock. Nothing will happen to it since it is made of tempered steel. Patience, patience, patience. Keep at it and the lock will turn.
For those who want to replace the lock cyl. it will be necessary to have a new CODED cyl. ready and the cap removal tool (202 589 00 14 00) handy. The tool must be in place before the striking of the lock procedure is done. There have been times that you only get "one bite of the apple" in turning the cylinder. The car would start but then when it is returned to the lock position, the key would not turn on subsequent tries, and I then had to repeat the process of making the lock turn again.
Below are instructions from M/B for lock removal and installation.