The car will warn you if your key fob battery is low
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From: Whitefield, NH
2015 C300 Sport: Palladium, Premium, Multimedia, Leather, BLIS
The car will warn you if your key fob battery is low
Not a major event, but the car does monitor the voltage level of your key fob battery.
I got a low battery warning on the main display the other day. The warning stays on while you're driving, which I found annoying since it disables the digital speedometer, and won't go away unless the car is shut off for several minutes.
I called my dealer to check on this and was told it is a legitimate low key fob battery warning. I was also told it's not unusual to have to change out the batteries every 6 months or so.
So, I did replace the CR2025 battery and the warning disappeared and all is well again. Changing the fob battery is very easy and can be done in less than a minute with no tools. I will, from now on, keep a supply of CR2025 batteries on hand since I think this will be a frequent occurrence. Probably not a bad idea to also keep an extra battery in the glove box in case this happens away from home.
I got a low battery warning on the main display the other day. The warning stays on while you're driving, which I found annoying since it disables the digital speedometer, and won't go away unless the car is shut off for several minutes.
I called my dealer to check on this and was told it is a legitimate low key fob battery warning. I was also told it's not unusual to have to change out the batteries every 6 months or so.
So, I did replace the CR2025 battery and the warning disappeared and all is well again. Changing the fob battery is very easy and can be done in less than a minute with no tools. I will, from now on, keep a supply of CR2025 batteries on hand since I think this will be a frequent occurrence. Probably not a bad idea to also keep an extra battery in the glove box in case this happens away from home.
Last edited by StanNH; Feb 27, 2015 at 08:41 AM.
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C400
Not a major event, but the car does monitor the voltage level of your key fob battery.
I got a low battery warning on the main display the other day. The warning stays on while you're driving, which I found annoying since it disables the digital speedometer, and won't go away unless the car is shut off for several minutes.
I called my dealer to check on this and was told it is a legitimate low key fob battery warning. I was also told it's not unusual to have to change out the batteries every 6 months or so.
So, I did replace the CR2025 battery and the warning disappeared and all is well again. Changing the fob battery is very easy and can be done in less than a minute with no tools. I will, from now on, keep a supply of CR2025 batteries on hand since I think this will be a frequent occurrence. Probably not a bad idea to also keep an extra battery in the glove box in case this happens away from home.
I got a low battery warning on the main display the other day. The warning stays on while you're driving, which I found annoying since it disables the digital speedometer, and won't go away unless the car is shut off for several minutes.
I called my dealer to check on this and was told it is a legitimate low key fob battery warning. I was also told it's not unusual to have to change out the batteries every 6 months or so.
So, I did replace the CR2025 battery and the warning disappeared and all is well again. Changing the fob battery is very easy and can be done in less than a minute with no tools. I will, from now on, keep a supply of CR2025 batteries on hand since I think this will be a frequent occurrence. Probably not a bad idea to also keep an extra battery in the glove box in case this happens away from home.
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From: Whitefield, NH
2015 C300 Sport: Palladium, Premium, Multimedia, Leather, BLIS
I would find it very unusual to have to change the FOB battery every 6 months! I've been driving cars with keyless entry & start/stop for several years and not once had to have to change the battery on a FOB. Granted some of those cars I didn't have longer than a year but others I had for just over 3 years and never changed the battery.
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From: London, Canada
2016 MercedesAMG C63S
I think it depends on how close it is to the car. If the car can sense it it will run the watery down. There is a feature that you can use to shut it off tho, if you're for example leaving on vacation or something... Hold the lock key down for 5 secs I think it is, and it will disable it. You can check the manual to find out the exact length of time to hold the button down and how to reactivate it, which is not hard.
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From: Whitefield, NH
2015 C300 Sport: Palladium, Premium, Multimedia, Leather, BLIS
Getting back to my original point, I don't think I've ever had a car before that actually warned you that it was time to change the battery on your key fob.
Poor battery life or not, that is a very useful feature.
Poor battery life or not, that is a very useful feature.
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From: NM
2023 AMG EQS
I don't own a W205, but I am pretty sure all you have to do is press "ok" on your steering wheel acknowledging that you are now aware that your battery is low.
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From: Manhattan Beach, Ca
C219 CLS / W220 † / W211† / W210 E55 † / W210 Brabus † / Hamann 540i † /
I was actually emailed this from my Mercedes rep a long time ago and found it funny that I saved it. Be nice to your keys guys! 
-Dont leave your Mercedes keys on top of the car or very close to the car.
A lot of people tend to park the car in the garage and place there Mercedes key on top of the car, leave in the car, on the tire or place near windshield. Do NOT do this! The sensor feedback will drain the battery.
-Use the Mercedes key fob to actually start the car now and then, placing the Mercedes key fob in the ignition and turning it over the "old fashion" way.
This will help sync and pair the fob again. *This does NOT charge the battery of the Mercedes key.
-Try not to abuse the Mercedes key.
Be nice to your Mercedes keys, do NOT throw or drop your Mercedes keys on hard surfices. This can damage, scratch or cause internal issues.
-Clean your Mercedes Key.
You clean your Mercedes Vehicle so why not clean your Mercedes Key. Our hands contain oil and dirt, so be sure the external and internals of the key are free of dirt and grime. *Do NOT get your Mercedes Key wet!
-Change your Mercedes Key yearly.
Be sure to bring your Mercedes Key to an Authorized Mercedes Dealership where we will gladly change your battery and reprogram. *Small dealer fee applies.
-Dont leave your Mercedes keys on top of the car or very close to the car.
A lot of people tend to park the car in the garage and place there Mercedes key on top of the car, leave in the car, on the tire or place near windshield. Do NOT do this! The sensor feedback will drain the battery.
-Use the Mercedes key fob to actually start the car now and then, placing the Mercedes key fob in the ignition and turning it over the "old fashion" way.
This will help sync and pair the fob again. *This does NOT charge the battery of the Mercedes key.
-Try not to abuse the Mercedes key.
Be nice to your Mercedes keys, do NOT throw or drop your Mercedes keys on hard surfices. This can damage, scratch or cause internal issues.
-Clean your Mercedes Key.
You clean your Mercedes Vehicle so why not clean your Mercedes Key. Our hands contain oil and dirt, so be sure the external and internals of the key are free of dirt and grime. *Do NOT get your Mercedes Key wet!
-Change your Mercedes Key yearly.
Be sure to bring your Mercedes Key to an Authorized Mercedes Dealership where we will gladly change your battery and reprogram. *Small dealer fee applies.
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From: Whitefield, NH
2015 C300 Sport: Palladium, Premium, Multimedia, Leather, BLIS
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From: Jersey
2023 GLC 300 SUV, 2006 BMW Z4M Roadster, 2006 Lexus RX400h
On my W204 both my keys started warning about the low battery just over a year old. The strange thing is that I never even used the second key and the battery died keeping it in storage far from the car.
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From: Milton/Westport, MA USA
me: 2015 SL400 & 2015 ML400; wife: 2022 GLC Coupe; daughter: 2017 GLC SUV
I just changed the battery in my W205 key for the first time and was surprised to only find one battery in there. All my other MBs took two. No wonder the batteries last longer in my W209, also with Keyless Go.....
Last edited by eddieo45; Nov 3, 2016 at 05:09 PM.
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From: Ontario, Canada
2016 C450 AMG, 2012 C350 4Matic Sport
While my 2009 C350 battery went about 18 months between changes, the 2012 fob needs a battery change every 6 months or so. Easy enough to do, instructions are in the manual.
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From: Whitefield, NH
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Well, it's now one and a half years since I first posted this. Yes, the low battery warning just requires a push of the OK button to clear it. The fob batteries can go anywhere from 6 to 9 months before they need to be changed, even if stored away from the car. Changing the batteries requires no external tools, and takes about a minute, so it's not a big deal. My biggest complaint is that the fobs are not linked to the car's memory, so opening the car with any fob does not trigger the seat memory. Standing there holding a seat memory button until the seat reaches its settings can be a real nuisance. This seems to be unique to MB, since every other car I've ever driven or owned has this function.
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From: Oklahoma
2016 C300 4Matic traded in for a 2022 E450 Coupe
Well, it's now one and a half years since I first posted this. Yes, the low battery warning just requires a push of the OK button to clear it. The fob batteries can go anywhere from 6 to 9 months before they need to be changed, even if stored away from the car. Changing the batteries requires no external tools, and takes about a minute, so it's not a big deal. My biggest complaint is that the fobs are not linked to the car's memory, so opening the car with any fob does not trigger the seat memory. Standing there holding a seat memory button until the seat reaches its settings can be a real nuisance. This seems to be unique to MB, since every other car I've ever driven or owned has this function.
Its not unique to MB, Volvo has about the same screwed up implementation, or lack of implementation, of seat memory and key fobs.
My old 2006 Acura had a perfect system in that regard. MB and Volvo, please replicate that functionality!
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From: Milton/Westport, MA USA
me: 2015 SL400 & 2015 ML400; wife: 2022 GLC Coupe; daughter: 2017 GLC SUV
Well, it's now one and a half years since I first posted this. Yes, the low battery warning just requires a push of the OK button to clear it. The fob batteries can go anywhere from 6 to 9 months before they need to be changed, even if stored away from the car. Changing the batteries requires no external tools, and takes about a minute, so it's not a big deal. My biggest complaint is that the fobs are not linked to the car's memory, so opening the car with any fob does not trigger the seat memory. Standing there holding a seat memory button until the seat reaches its settings can be a real nuisance. This seems to be unique to MB, since every other car I've ever driven or owned has this function.
BTW, when you say "every other car I've ever driven or owned has this function" I assume you mean to exclude the Datsun 2000 and Mazda Miata but did the Z3, A4's and S60 really adjust your seat based upon which key you carried??
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From: Ontario, Canada
2016 C450 AMG, 2012 C350 4Matic Sport
Agree 100%. This feature worked great on my 2005 TL. 11 years later MB still hasn't added it.
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Benz
I thought it'd be quite common with cars that offer comfort access. I had a 2010+ Camry with comfort access and it displayed low-battery warnings for the fob.
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From: Whitefield, NH
2015 C300 Sport: Palladium, Premium, Multimedia, Leather, BLIS
Stan, I didn't notice how old the thread was when I revived it, lol! I was pulling my hair outta my head trying to open the key fob the way I've done it on 6 other Benzes since 2003 and hoping to get a clue!
BTW, when you say "every other car I've ever driven or owned has this function" I assume you mean to exclude the Datsun 2000 and Mazda Miata but did the Z3, A4's and S60 really adjust your seat based upon which key you carried??
BTW, when you say "every other car I've ever driven or owned has this function" I assume you mean to exclude the Datsun 2000 and Mazda Miata but did the Z3, A4's and S60 really adjust your seat based upon which key you carried??
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From: UK
C Class 200 sport petrol auto
The W205 keyfob seems to have an unhealthy over range to unlock the doors or to release the boot. It must be at least 150m and that is even around corners. No wonder thieves with laptops are managing to steal the codes as they don't even have to be close to the car.
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benzw205
The W205 keyfob seems to have an unhealthy over range to unlock the doors or to release the boot. It must be at least 150m and that is even around corners. No wonder thieves with laptops are managing to steal the codes as they don't even have to be close to the car.
I wonder if thieves have all the codes for all the new cars ? Any report of a C-class stolen without being broken ?
Thanks.
