Replace Damaged/worn/Remote Key Fob Case.

If your 'A' Class is an early model then there is every chance that your remote key casing is badly worn or even damaged . New remote Keys complete with the internal components coded to your car in Germany now cost close to 200.00 9/7/2011
Or in the case of later models the key is damaged by dropping which happens more times than we are prepared to admit.
Well there is now an answer to this problem , if you have a key tucked away that works but you can not use because of the damaged case you can now replace the case only.

You will have seen on my previous pages me saying 'do not purchase Mercedes-Benz 'A' Class keys off e-bay or any where else for that matter as they will not work.
That is still true and nothing should convince you otherwise,
unless you can utilise the components of both your own and a second hand key .

However if you purchase a remote key case only (empty Case) with no components it will be fully compatible with your internal components being almost identical to the original Siemans/Mercedes-Benz reomote key fob,
That being the case, the internal mechanism in your existing key fob can now be transferred to the new case. However it is a job over which you should take your time, one because the new case does not come with instructions and 2 any damage to the internal components is likely to prevent it working even though installed in a new case.
This swap of components is only appropriate where the key is fully functional to start with but is suffering from a badly worn or damaged case.
Changing the case of a non functional key will not make it work.
But I will make a further suggestion at the bottom of this page.

The new case will comes apart easily, it not having been sealed, this should not be the case with your existing remote keys, the two halves should be found sealed. in fact they can be difficult to open unless you take your time.

The new case will have severn parts:-
1. Top half of case
2/3 Bottom half of case, which has a removable section for access to the batteries as with your present key fobs.
4. The Metal key carrier complete with a blank blade
5. The key return spring

6. The flick button to release the key from the fob.
7. Reflective red section which covers the infra-red transmitter.

There are very slight differences between this case and the original siemans/Mercedes-Benz two button remote key case.:-
1. The red reflector is slightly different which may make the battery indicator light slightly harder to see.
2. There is no information on the case to indicate how the batteries should be fitted.or details of the fob specification.
3. It does not complete with the small white inner tray as shown in the photograph, 3rd from the bottom of this page , this mini tray may be transferable from the damaged /worn key case if required .

The key blade fitted to the case is uncut, you can either have this cut, or you can just transfer the key blade and holder from your existing damaged remote case.
If the chrome is damaged on your old key blade holder then you can remove the key compatible with your car and fit it to the new holder .

This is done by tapping out the securing pin A with a very small drift, removing the new blade from the holder, simply pull, fit your own blade and replace the pin. However note that the securing pin can only be seen and thus removed when the key blade is folded at right angles to the case.

If you have reason to purchase one of these remote key cases then I strongly suggest you practice taking it apart and re-assembling several times before you do the actual transfer.
This is because the parts are small and need to be assembled correctly for the key blade to lock closed and spring back out when the button is pressed.
If the spring is not inserted correctly this will not happen and it is too late to alter it if you have already sealed the case which you will finally need to do.

When you reach this stage and have ensured the key is working with the car, then a glue such as Araldite, two part glue would do the job , it will take a few minutes to go off but will give you time to make small adjustments. if you examiun the tywo parts of the case you will see the contact points which will best secure the key against fallin ap[art and loosing the transponder pea.


Locating the spring correctly :- Inside of the key release button there is a location slot for the spigot on the top of the spring, Place the button on the spring and rotate , you will feel the tail of the spring engage in the slot.
The projecting tail at the base of the spring locates in a slot on the bottom half of the casing supported by the spigot which projects from the bottom half of the case.
With the spring inserted into the button locate the spring complete with button onto the spigot on the lower half of the casing, Now place the key blade and holder on to the button. you will need to align and adjust this tto suit the slots in the key blade holder with the projections on the button.

Note that as in the photo, right. The blade is beyond parallel to the top of the key case and should be positioned as in the photo right.
This must be located in this way to enable the lugs to be engaged on the button
also by positioning it in this spring tension will be applied as the key blade is straightened in the next stage of assembly.

Now place the top half of the casing onto the button and align the top half of the case with the bottom half. apply gentle pressure againd the release buttomn spring.
Now gently straighten the key blade and holder, apply slight pressure to the casing
we do not want to fully close the case at this point.
Now place the red reflector into the top of the key open slightly if neccessary, when in position fully close the case.
With the casing held closed , test the folding of the key blade, ensure it locks closed in the side of the case.
Press the release button ensure the blade springs from the side of the fob goingf to the locked position.

Only when you are satisfied that you are familiar with the assembly procedure, remove and transfer the components from the damaged key fob.

Avoid touching the components on the printed circuit board as much as possible, wear glove if available.( moisture on your hands will be transferred to the components or avoid touching the PCB.(Printed circuit board) hold only the edges of the board.
remember as well as the main board the transponder pea must also be transferred, although I indicated the location of the pea I have not got a photograph which shows it in the unit, it is small and without it your key will not work, a missing or incorrect transponder pea will result in the instrument cluster displaying the message, 'Start error'

E shows the point where the projection on the bottom of the spring engages with the lower portion of the case.

G Is the pin that secure the key blade in the key holder.
The pin is re-uasable if care is taken tapping it out.
Take care not to loose it, it is minute in size. size.

F indictes the location point of the transponder pea. lightly glue in place, keep glue to a minimum.

The three yellow marks indicate the lugs on the button which must engage in the key blade holder

Having mounted the key blade holder on the button and spring, place the top half of the case in place and over the button, Holding the case steady, move the blade in line with the case, the two halves of the case can now be closed, do not fully close the back of the key at this point, as we have still to put in the red reflector. case

Leave fitting the red reflector your last assembly job, Bearing in mind that the transponder pea is in this immediate area, and having satisfactorily installed the other components, leave the back edge of the case open by 1/8" (3-4 mm)

Having carefully applied a small quantity of glue to the contact surfaces place the reflector in position and close the back of the remote key case.
Clamp closed using a rubber band until the glue is fully set. Avoid getting glue on the new case

When fitted the PCB into the bottom half of the case ensure battery contact pins locate in the slot provided and are not bent. cont

Ensure the battery terminals and batteries are clean before placing into remote case, moisture on your hands may damage the components.

Other Possibilities
Now that a suitable replacement remote key case available, other anaenues open up for the possible contruction of a working key for you car, there is the possiblity of purchasing a second hand key removing the PCB from the key and placing it into the new case. The transponder pea from the purchased/second hand key should be discarded and the pea from your own defective none working key inserted in the new case along with the replacement PCB.
The now assembled not sealed, remote key will almost certainly want re-synchonising with your car before the central locking will work. The procedures for undertaking this task are on the previous page (page 6)

If you do still find the newly constructed key does not work, then bear in mind it like your own key may contain defective components.
although the key should operate the remote locking after synchobnising , bear in mind that the key blade must be changed from your own defective remote key or you will simply get a 'start error' message.

Even if this trial does not work the new case can still be salvaged, as you can test the remote before sealing the case.
If the trial does not work then all you have lost is the cost of the second hand key, so do not pay over the odds as you will not be able to return it, even if that was acceptable to the seller!
Therefore there is little to be lost in undertaking this trial.

Please note I have not undertaken this task myself and so cannot say if it will work or not , but as far as I'm aware the only difference in owners two button Mercedes-Benz keys is the coding of the transponer pea and the blade which can be switched with your own.

Good luck why not be the first to give it a try, little to lose and all to gain
if you can get a defective key working.
Please let me know the outcome and how you got on Thanks. Lofty

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