mitul

Hi Everyone,

Can anyone please tell me how I may be able to change the battery in my smart key. Is there a step by step instruction on how to crack it open?

Thanks

Mitul
1998 E430

awiner

It should be deatiled in your owners manual.

RUSSH

When you slide the piece aside to get the blade out, you should see a white or grey piece in there. Get a paper clip or something of that size and gently push it, as you do that slide the whole bottom piece of the key out.

Darkmann

No, it's not detailed in the manual. What you have to do is this:
1) Take out the metal spare key from the electronic body
2) At the top of the opening, you'll see a small plastic "latch"
3) Use a small screw driver or pin to pust against this HORIZONTALLY (i.e., with key sensor facing down, push against this plastic piece horizontally)
4) As you push, pull the top portion of the electronic key in the vertical direction. It should come out and allow you to replace the battery.

ideaman4u

Darkmann,
I thought I had the trick figured out when I read your posting confirming my discovery. BUT top cover does not seem to want to cooperate. Just how much pressure SHOULD it take to remove top cover? I do NOT want to break the damn thing!

saintz

You can find a replacement (used) key on eBay for about $20. The electronics in the used key are worthless, they can't be recoded. But the shell is compatible and easy to swap. So if you break the shell trying to open it, it's not the end of the world.

Try working it back and forth rather than trying to just push really hard.

ideaman4u

saintz,
Thanks for the encouragement. I found some pictures on the internet showing the chrome fob I have being disassembled. I wasn't exactly sure what came out of what. Problem complicated by the fact that I bite my fingernails and therefore could not use to get under the top. I got a sharp small flat blade screwdriver and used it to leverage the top while sliding the interior latch using the head of the blade key. Eventually, it slid up enough to clear the latch. Voila! Electronics (and batts) accessed! Thanks again for your kind assistance.
Ideaman4u

raymond g-

applicable for 1 and 2gen Smartkey


3gen

ideaman4u

Raymond,
The lower picture series applies to the key provided with my "new" (2002) C240. Many thanks for posting. I am sure will help other poor souls who are confused with battery replacement procedures for this particular electronic key.

Musikmann

Thanks too Raymond. I've never seen the instructions for the newer chrome keys.

Darkmann

The latch is spring loaded so you don't need that much force. It's just tricky to pull out because the same hand holding the key is the one you need to take the cover out. I just push the nail on my index finger in the seam and pry out the cover.

ideaman4u

Gotcha!

tresean1

Hi there, I know this is an old post but I am finding myself in this dilemma right now with an older Smart key.

I'm very familiar with how to change the battery, but changing the circuit board is where I'm having trouble with. I know you have had success in changing it, but I cannot seem to find the "white retainer clip" that is mentioned. Here is a photo of my key. I am a bit stuck as to how to remove the circuit board. What tool can I use that will unlock the retaining clip, and what exactly am I looking for?

Any help is greatly appreciated, as I am very stumped right now.