Key fob battery died with no warning notification
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Senior Member
Joined: May 2019
Posts: 305
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2007 S550
Key fob battery died with no warning notification
My key fob battery died on me today and didn't give me the dash notification. I've seen it before. It says "Replace Key Battery". I didn't get that. Just no response from the key fob on button pushes. It did start though. I have Keyless Go so it did the push button thing just fine. Can this message be shut off in the options somewhere? If so, I want to turn it back on.
I pulled out both batteries and tested them. The top one had 2.9V and the bottom one had 2.7V. It surprising that such a small deviation from full will cause the key fob to stop working. I replaced them with the thicker ones(2032) and carefully wiggled the key fob back together. Works great now. I think I got 5 months out of that last set of batteries.
I pulled out both batteries and tested them. The top one had 2.9V and the bottom one had 2.7V. It surprising that such a small deviation from full will cause the key fob to stop working. I replaced them with the thicker ones(2032) and carefully wiggled the key fob back together. Works great now. I think I got 5 months out of that last set of batteries.
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Joined: Dec 2011
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W212 FL
I can get maximum 10-12 months using known brands with those 2032s . I have not come across before a key fob battery notification doesn't pop out or key fob stops working due to a low battery without a warning . Normally , it should warn you way before it goes bad and as you said "Replace Key Battery" message appears
Super Member
Joined: Nov 2021
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From: Hong Kong, China
2021 S450 4Matic
If I recall correctly, the key fob has a red light flashing when you push the button. When battery is weak or low in juice, the red light gets dimmed. This is a good indication that you should replace the battery.
Secondly, when battery is weak, you often have to get close to the vehicle to open the door and sometimes you might need to press the button a few times. This also indicates weak battery.
As you have learned, do not rely solely on the 'Replace Key Battery' warning. Take preemptive strike.
Secondly, when battery is weak, you often have to get close to the vehicle to open the door and sometimes you might need to press the button a few times. This also indicates weak battery.
As you have learned, do not rely solely on the 'Replace Key Battery' warning. Take preemptive strike.
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Joined: Oct 2021
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From: Iowa
2008 CL550, 2022 EQB 300, 2023 EQS 450 4Matic
Speaking of key fobs, I bought a new old stock key fob yesterday, to have as a spare/backup. I believe these are no longer made, and have not been for a while. Smart move, or waste of money? I plan to keep my car as long as I can get it to run. I know with some of the Mercedes from the 1990's, it would be gold to come across a new key fob.
My key fob battery died on me today and didn't give me the dash notification. I've seen it before. It says "Replace Key Battery". I didn't get that. Just no response from the key fob on button pushes. It did start though. I have Keyless Go so it did the push button thing just fine. Can this message be shut off in the options somewhere? If so, I want to turn it back on.
I pulled out both batteries and tested them. The top one had 2.9V and the bottom one had 2.7V. It surprising that such a small deviation from full will cause the key fob to stop working. I replaced them with the thicker ones(2032) and carefully wiggled the key fob back together. Works great now. I think I got 5 months out of that last set of batteries.
I pulled out both batteries and tested them. The top one had 2.9V and the bottom one had 2.7V. It surprising that such a small deviation from full will cause the key fob to stop working. I replaced them with the thicker ones(2032) and carefully wiggled the key fob back together. Works great now. I think I got 5 months out of that last set of batteries.
Out Of Control!!
Joined: Nov 2018
Posts: 11,463
Likes: 5,354
From: San Francisco Bay Area
2019 C63CS
It's not uncommon for these coin batteries to suddenly die w/o time for a low battery warning. You don't know how long they sat on the shelf and some are of poor quality. I just recently had a device with a 2032 battery suddenly die on me, even though the last battery report said it still had about 73% state of charge. They don't always deplete linearly.
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Thread Starter
Senior Member
Joined: May 2019
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2007 S550
Speaking of key fobs, I bought a new old stock key fob yesterday, to have as a spare/backup. I believe these are no longer made, and have not been for a while. Smart move, or waste of money? I plan to keep my car as long as I can get it to run. I know with some of the Mercedes from the 1990's, it would be gold to come across a new key fob.
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MBWorld Fanatic!
Joined: Oct 2021
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From: Iowa
2008 CL550, 2022 EQB 300, 2023 EQS 450 4Matic
Bought it on Ebay for $175. I know it would need programming, so maybe another $175 to get it working. Or, maybe Benz Ninja could do it (?), as I'm about to sign up with him.
Super Member
Joined: Dec 2018
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From: Washington, DC
2007 S600, 2007 Chrysler 300 SRT8, 2000 C5 Corvette, 2017 Mustang GT, 2023 300C, and a 2019 Lincoln
Yup, when I bought mine in 2018 I negotiated for two key fobs and the Mercedes dealer ordered a new one, programmed it, and charged the dealer I bought it from $450. He told me that was discounted because it was between two dealers. Glad I did the deal the way I did. $$$$
Thread Starter
Senior Member
Joined: May 2019
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2007 S550
Kind of a Catch 22 there. The dealer won't program it because you didn't buy it from them. They also won't sell you one without programming it to your car because it's a theft relevant part. Benz Ninja could do it if your ignition switch or whole car was at his shop. Or an Indy shop could do it. From what I understand, none of the Keyless Go stuff will work if you do it outside of the dealer.
MBWorld Fanatic!
Joined: Oct 2021
Posts: 1,196
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From: Iowa
2008 CL550, 2022 EQB 300, 2023 EQS 450 4Matic
Kind of a Catch 22 there. The dealer won't program it because you didn't buy it from them. They also won't sell you one without programming it to your car because it's a theft relevant part. Benz Ninja could do it if your ignition switch or whole car was at his shop. Or an Indy shop could do it. From what I understand, none of the Keyless Go stuff will work if you do it outside of the dealer.
In general, it has been surprising/sort of funny that I've bought some new OEM parts recently that have literally been the last 2 or 3 in the world, or in one case the last in the world. This stuff will never be made again. It is hard to know where to draw the line on my car, as I've added more and more parts to it...way beyond what would be rational economic thinking.
