repairing broken W202 Key fob.

[anyweb]

hi all, I'm posting this incase any of you have a similar problem, sure saved me some bucks and only took an hour or so to fix.

if you wish to discuss this post then do so here > http://forums.mercedesclub.org.uk/showthread.php?t=26888

Problem:-

* key won't open the car
* key LED won't light even with known good batteries
* chance that you may have dropped the key recently

Solution:-

In my case, the solution to the problem became evident when I took the key apart (it should prise apart quite easily, if not use gentle force), as a piece of it fell to the floor when I got the two halves open. The piece that fell on the floor was an electronic switch which had become loose from its 4 soldered leg joints.

So what do you need to accomplish this ?


* steady hand
* bright light
* a magnifying glass to see the solder joints etc..
* a soldering iron
* some solder wire

(see below)

Here is my broken key in it's disassembled state.

You can see the switch is not attached to the circuit board, and thus, the key's infrared functions cannot work.

I examined the detached switch with a magnifying glass and could see the legs were bent so I re-arrangfed them gently to be more in line with the 4 contacts on the circuit board (be gentle, if any of the legs snap off you are going to find it VERY hard to fix as they are so small).

I then aligned the switch to it's mating points on the circuit board, at this point, I held it very tightly against the board and had my soldering iron heated up for the next stage, soldering.

Once correctly aligned I carefully got a blob of solder on the end of the soldering iron and 'touched' it briefly to each of the 4 legs in turn until they clearly had solder in place. Be careful with the soldering iron, you could end up getting solder on any of the other contact areas around the switch and that wouldnt be a good idea as there are quite a few 'lines' running around it.



Here's what they looked like after the soldering process

Finally I had to reassemble the key at this point you can put the two batteries back in and you should see the familiar LED light up after a few seconds of pressing *SUCCESS*

Please note:- when you have the key all back together again, you may notice that it doesnt 'flick out' as it used to, this is simple to fix, open the key again in two halves and 'wind' the key around its centre point ONE FULL TURN in the direction of force, then place the two halves back together again.


One last note, after doing this job you'll have to RESYNC the key to your car, to do so, do as follows,

SYNCHRONIZING LOCK SYSTEM
Aim the transmitter of the remote control at the receiver in the interior mirror and press transmitter button briefly twice. Turn the key in the steering lock to position 2 within about 30 seconds.

Aim the key at the mirror again and press once, The GREEN or RED mirror led should light (red when you close, green when you open). If they both flash together at the same time then try again. If they continue to flash together then replace the batteries and try again, if they flash alternatly (red/green/red/green) then you may have some other problem like the car battery).

cheers
anyweb

 

[Blobcat]

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