Ceric

I am coming from BMW (E46 3 series and E39 5 series) and am about to buy my first Mercedes. Would love a C350 but can't seem to find one with the options I want, so it will be a C300. However, that's besides the point. What I am wondering about is the Mercedes key itself. Since the battery is replacable, the key is not sealed. And in the videos I've seen, the key does not seem to have any gasket or water barrier between the battery compartment, the key electronics, and the outside. Seems like just a plain plastic snap-on cover. My question is, how waterproof is this key? Can it get wet? I am used to taking my BMW key, slipping it under my wetsuit and going swimming with it. I even go scuba diving with it, and it never gave me any problems. How about the mercedes key?

Adi-Benz

Nope, its about as good as the seal with the compartment is. Which basically means, it can handle a bit of water, but is not waterproof. I'd just get a case, not really a big selling point imo.

Ceric

Is there a way to leave the key somewhere hidden, outside the car, without activating the keyless go system?

If you take the blade key out of the keyfob, and leave the keyfob inside the car, then lock the car with the blade key. Will the keyless go system be deactivated, or can someone just walk up to the car and open it and drive away?

Adi-Benz

That's actually a good idea, I don't have keyless go so maybe someone with it will be able to chime in.

Sentosa

I use that system on my GLA when I go surfing. Put the blade key on a lanyard around my neck and leave the fob in the car. Works for me.

Shimee

If someone breaks into the vehicle they will be able to start it and drive away. The blade has no connection to the keyless go system.

Like others have said, the key is as good as the seal around the battery. The rest of the key is ultrasonically welded together so those seams are waterproof. I don't believe Mercedes-Benz has done any water ingress testing on the key, as there are no markings inside it indicating what it is rated to nor does the manual say anything about how water resistant it is. You should reasonably expect 3 feet for 30 seconds but definitely no more as the water pressure would increase and defeat the battery seal.

Ceric

I guess I could take out the keyless-go button out of the ignition, and hide the key itself somewhere smart inside the car. The only way they would be able to drive away after breaking in then is if they could find the key. I will have to test this out as soon as I have the car.

Shimee

Easiest solution would be a small resealable food bag or one of those pouches that you can get for cellphones. Both would allow you to hold the key in exactly the same way you're used to. Although the latter would be more water tight at greater depths.

Lee Eastham

Just put my second key through the washing machine, I found it in the door seal. Figured that was going to be an expensive mistake and went about discovering how to get the battery out. I was pleasantly relieved to find the rubber seal had done it's job and there is no sign of moisture inside the key. I've left it to dry anyway but it looks like I had a lucky escape!
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