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2002 C240
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11 Posts
Discussion Starter #1
My key stopped working this week for locking and unlocking the doors and trunk. I've had my C240 since February and have had no problems with the key before this. Is there a battery that may need to be replaced?

Thanks for your help.
 

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C 240 2002
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9 Posts
key...

sometimes you have to figit with the removable metal key that is used for the glove box or trunk. One day my key stopped working too, but after i moved around the metal key, it worked fine. From time to time i have to do this too, to get it working.

elijah
 

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2001 C320
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12 Posts
I had a problem early on with the keys not working for my C320. It was intermittant at first and the dealer could not verify the problem. Then they completely stopped working for remote functions. (I thought it was the battery but it turned out not to be the case.) I had to have the keys replaced twice before they finally worked. Hope yours is more simple and the battery is the solution.
 

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2002 C240
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11 Posts
Discussion Starter #4
Thanks .elijah. and Cmomma

.elijah. - The removable key sounded like it might be the problem since I had recently used it. I tried jiggling it and even removing it completely. I did get the unlock door feature to work consistently but the lock door and unlock trunk function still do not work at all with this key. Darn.

Cmomma - It sounds like I may have to get this key replaced and hopefully only once not multiple times like you. The other one is working fine.

I wonder if carrying it loosely it my purse might have scratched the sensor or something along that line.

I'll call the dealer today. It doesn't sound like too big of a deal but I would hate to be stuck somewhere without the removable part and not be able to get into my car...

Thanks again.
 

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E500S4, C240; Sold ML320, '72 280SE, '67 280SL, '86 300E, '87 300SDL
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383 Posts
The dealer replaced one of the keys when it started to do this. It took a few weeks to ord...

The dealer replaced one of the keys when it started to do this. It took a few weeks to order it but it fixed it. A small slap [;)] on the key would sometimes made it work when it was acting up.
 

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1999 SL500, 2009 E350S 4Matic, 1992 300CE (sold)
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143 Posts
Common problem

For soem reason many C classes are having key probelems. Dealer will diagnose and order you a replacement.
 

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Glenda, the dealers don't seem to generally be very competent in diagnosing problems lik...

Glenda, the dealers don't seem to generally be very competent in diagnosing problems like this.

One thing that is happening with these keys is a weak contact spring with the battery. This can easily be fixed by YOU and will more likely than not solve your problem.

Open the key to get to the battery (look in your owner's manual for instructions). When you see the battery, you will see a thin, straight contact bar holding it in. If you lift the contact bar, and gently bend it so the middle of the bar contacts the middle of the battery more firmly, you likely will solve your problem.

I was in line at the parts counter one day and a lady came in with a "dead" key. The parts guy took out the battery, put in a new one, still didn't work (the red light didn't light up). He put the old battery back in and pronounced the key dead. Had to order new ones, come back for reprogramming, etc.

I took her key, and in 30 seconds bent the contact a little, put it back together and it worked fine. She went away happy!
 

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2013 ML350, 2004 ML350
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335 Posts
Happened to me!!!

That happened to some ML owners
YEP, sure did to me!!! on both my ML (I believe 4 keys) and C (3 keys)
 

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2002 C240
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11 Posts
Discussion Starter #10
I will try this suggestion today.

Thanks SoCalC240/6. That sounds a lot easier what the dealer wants to do.

I went to the dealer and told them the problem. Of course the key worked fine while I was there. I explained it was an intermittent problem and that I never knew when the key would work and when it would stop working.

I explained that several people on the MBenz forum had to have their keys reordered with this same problem. He said that because the car is still under warranty that they must run diagnostic tests to look at the codes. They can not just order a new key. This means I have to leave my car with them for an entire day to run these tests. That's not a big problem, it just seems like an awful lot of work and time for a faulty key.

I am going to read the manual about taking the key apart this evening. I don't want to actually do it until the key stops working again. That will tell me if this is my problem. It sure sounds plausible.

Someone mentioned the problem could be too many keys on the same ring. I only carry this key and my credit card on my key ring so I don't think that is the problem with my key.

Thanks again to everyone for all the suggestions. I will post again as soon as I have a definitive answer.
 

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Good luck. To clarify, when you take the battery out, you'll see that the thin metal st...

Good luck. To clarify, when you take the battery out, you'll see that the thin metal strip that holds it in place is basically straight. What you want to do is bend it slightly so it forms a very light U shape.

This puts the center of the strip in better contact with the center of the battery.

This is a problem that happens with all the keys, the old ones and the replacement ones.

(That being said, the keys seem to have other problems sometimes, too. So there is no guarantee this will fix it - but it only takes a couple minutes and is worth a try!)
 

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Taking it out and bending the flat battery connector seemed to help a little for me.

I've only tested it out twice so far and the second time it worked after a few tries.

I'm half convinced that's the issue.





dan
 

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Well I had the same problem with mine...when I asked the dealer about getting the new version of the key which seems to be more reliable....they asked for 100 euro!!! then I took it to an indian who fixed both keys for 2 euros....
 

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2008 ML320 CDI
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38 Posts
Good luck. To clarify, when you take the battery out, you'll see that the thin metal strip that holds it in place is basically straight. What you want to do is bend it slightly so it forms a very light U shape.

This puts the center of the strip in better contact with the center of the battery.

This is a problem that happens with all the keys, the old ones and the replacement ones.

(That being said, the keys seem to have other problems sometimes, too. So there is no guarantee this will fix it - but it only takes a couple minutes and is worth a try!)
One of my keys had completely stopped working and I had basically written it off after changing the batteries had no effect. A month later I decide to do a little searching and ran accross this nearly 10-year old post. Bending the metal strip worked like a charm! Key is perfect now. Don't know if you're still around the forum, but thanks SoCalC240!!!
 
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