Aux Battery affecting Key Fobs?
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Joined: Jan 2023
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GLK250
Aux Battery affecting Key Fobs?
I've had my 2013 GLK250 for about 4 years now (bought used), and the other day received the "Auxiliary Battery Failure" message. I actually didn't even know that the car had one, but now I know! I located it, removed it, and put a volt meter to it. Dead. Like...0 volts! New battery on order, so not a big deal. HOWEVER, before the message appeared, neither of my key fobs would work, even though the batteries show 2.97V. I know that's not brand new, but still high. As I was doing some research on the purpose of the aux battery, I'm now wondering if the inop key fobs are related to the aux battery. I guess when the new battery arrives, I'll know for sure, but wondering if someone knows. Thanks! This is my 1st post here, so go easy on me.
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Out Of Control!!
Joined: Sep 2018
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From: unbegrenzt
2017 GLE350 4MATIC
Measuring voltage on batteries is meaningless. instal new fob batteries, aux battery and main battery if it has not been changed during your ownership. Less then perfect batteries can cause many "unexplained" electrical oddities on modern vehicles, which are rolling computers.
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From: Blue Oval City, TN
2013 GLK 350
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Joined: Jun 2021
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From: South Texas
2014 GLK350 base model (active) ; 2001 E320 base (retired); 2001 Wrangler soft-top
I've had my 2013 GLK250 for about 4 years now (bought used), and the other day received the "Auxiliary Battery Failure" message. I actually didn't even know that the car had one, but now I know! I located it, removed it, and put a volt meter to it. Dead. Like...0 volts! New battery on order, so not a big deal. HOWEVER, before the message appeared, neither of my key fobs would work, even though the batteries show 2.97V. I know that's not brand new, but still high. As I was doing some research on the purpose of the aux battery, I'm now wondering if the inop key fobs are related to the aux battery. I guess when the new battery arrives, I'll know for sure, but wondering if someone knows. Thanks! This is my 1st post here, so go easy on me.
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It was like that for over a month - I never use ECO mode (switch if off as I'm starting it), so wasn't too concerned about replacing it immediately.
But after a month of having to tap OK to dismiss the message, I went and bought a new Aux battery at Oreilly Auto Parts.
I replaced it in the parking lot (about 5 minutes) to save a trip back to Oreilly and core charge
BTW, it never affected the use of the key FOB.
Last edited by calder-cay; Jan 10, 2023 at 11:22 AM.
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From: New Hampsha
'17 GLS450, '14 GLK250, Grandpa's Roadster
Don't you mean Dollar store? I haven't seen a dime store in about 60 years.
It's a 3 volt battery. If it shows less than 3 volts it's probably bad. A new one may show as high as 3.4 volts.
It's a 3 volt battery. If it shows less than 3 volts it's probably bad. A new one may show as high as 3.4 volts.
Last edited by John CC; Jan 10, 2023 at 10:19 AM.
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From: NYC
glk
I've had my 2013 GLK250 for about 4 years now (bought used), and the other day received the "Auxiliary Battery Failure" message. I actually didn't even know that the car had one, but now I know! I located it, removed it, and put a volt meter to it. Dead. Like...0 volts! New battery on order, so not a big deal. HOWEVER, before the message appeared, neither of my key fobs would work, even though the batteries show 2.97V. I know that's not brand new, but still high. As I was doing some research on the purpose of the aux battery, I'm now wondering if the inop key fobs are related to the aux battery. I guess when the new battery arrives, I'll know for sure, but wondering if someone knows. Thanks! This is my 1st post here, so go easy on me.
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From: South Texas
2014 GLK350 base model (active) ; 2001 E320 base (retired); 2001 Wrangler soft-top
It depends ... is your Aux Battery in the spare tire area as with GLK 350's or is it a 250 ??
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On our GLK350 (spare tire area), took me 15 minutes, by removing the battery cover, and using standard metric sockets.
Can't speak for the 250...
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On our GLK350 (spare tire area), took me 15 minutes, by removing the battery cover, and using standard metric sockets.
Can't speak for the 250...
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GLK250
Super easy, but a tad awkward. The whole process of removal took maybe 10 minutes, if that.
1. Remove 3 torx screws from the front of the "kick panel" under the steering wheel. This will allow you to get your hand underneath the dash to manipulate the position of the battery. No need to remove the panel, just be able to get your hand up there.
3. Remove the plastic cover on the left side of the dash. I used plastic tools that are made for this purpose and don't mar the surfaces.
4. Remove the bolt (10mm) that becomes very obvious once you remove the plastic panel. That screw holds a tray in which the battery is cradled.
5. Use both hands to position the battery (it's behind some felt) such that you can pull off the terminals. This is why you removed the bottom panel.
6. Use both hands to remove the battery from the cradle. I think you can probably also remove the cradle, but there's not a need.
7. Now just wriggle the battery out of the square hole on the side of the dash.
1. Remove 3 torx screws from the front of the "kick panel" under the steering wheel. This will allow you to get your hand underneath the dash to manipulate the position of the battery. No need to remove the panel, just be able to get your hand up there.
3. Remove the plastic cover on the left side of the dash. I used plastic tools that are made for this purpose and don't mar the surfaces.
4. Remove the bolt (10mm) that becomes very obvious once you remove the plastic panel. That screw holds a tray in which the battery is cradled.
5. Use both hands to position the battery (it's behind some felt) such that you can pull off the terminals. This is why you removed the bottom panel.
6. Use both hands to remove the battery from the cradle. I think you can probably also remove the cradle, but there's not a need.
7. Now just wriggle the battery out of the square hole on the side of the dash.
