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2009 SLK350
460 Posts
Discussion Starter · #1 ·
The unlock button on my main key fob suddenly stopped working, although the lock and open trunk/boot functions worked fine. Since I had replaced the batteries a few months ago I figured it was only the unlock side on the circuit board. I took apart the fob and inspected it under a low power microscope. Circuit board and microswitch looked fine, so I looked at the inside of the key fob shell and noticed that the unlock button was missing the spiral and not pushing down on the microswitch, (See 1st pic). I cut a small strip of masking tape and folded it a few times with the adhesive side out so it would stay in place. Made it just thick enough to fill in the missing space. Put it back together and now works. YES!!!

My spare key fob has never worked since purchasing my car from the previous owner so with this knowledge I took it apart to see if this was also the issue. Shell was fine so I started looking over the circuit board to see if anything was wrong with it. All looked fine but I did notice that the outside contact on the circuit board was worn through and was not contacting the battery tray. (See pic 2). I soldered a small dab on the contact and now all works as it should. (See pic 3)

I now have 2 working key fobs. YES!!!

Saved myself about $200+ per fob.



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