2006 E320 CDI auxiliary battery not getting charged
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Super Member
Joined: Apr 2007
Posts: 633
Likes: 48
From: USA
2006 E320 CDI
2006 E320 CDI auxiliary battery not getting charged
I hadn't driven the car in many months but kept the main battery (G1) located in the trunk, float charged. I thought that it would also charge the auxiliary battery under the hood (G1/7) battery but it didn't/doesn't. I started the car and let it run for 30 minutes, while the engine was running the voltage on the aux battery was 8.0v. In the charge circuit there are only a few components involved. N82 controller (in the trunk near the main battery), K57/2 relay (under the hood mounted on the firewall under a rain shield and F30 fuse, it suppose to be near the auxiliary battery, but I can't find it. When the relay energizes it provides 12v to the aux battery. I haven't tested anything yet, except I checked both terminals of the K57/2 relay, 12v on the supply side, and the other terminal has the aux battery voltage. So the relay must not be energizing.
Where is that F30 fuse??? Anyone know?
Thank you
Where is that F30 fuse??? Anyone know?
Thank you
Senior Member
Joined: May 2014
Posts: 485
Likes: 31
From: Concord, CA
'13 E350 . M276
F030 should be inside car, dashboard - left side
https://mbworld.org/forums/e-class-w...les-chart.html
https://mbworld.org/forums/e-class-w...les-chart.html
Thread Starter
Super Member
Joined: Apr 2007
Posts: 633
Likes: 48
From: USA
2006 E320 CDI
@Stuttgarten, the F30 that you pointed to is for the data link ... not the F30 I am trying to locate. Apparently MB has named two fuses F30. I looked in the WIS but I couldn't find a picture of its location. Has anyone here worked on the aux battery circuit? Where oh where is that F30 fuse, which I believe is actually a circuit breaker. Thank you
Thread Starter
Super Member
Joined: Apr 2007
Posts: 633
Likes: 48
From: USA
2006 E320 CDI
Well I found F30, it is taped to the aux battery positive cable about 3" down from the battery post. You need to remove the aux battery to access F30. It measures 2.5 ohms, but you need special Fluke probe clips (TL82) to reach inside of the connector to measure the ohms. I backprobed (again special Fluke probes TP40) the K57/2 relay connector and its getting voltage and energizing now. 14.0 vdc is now being measured at the aux battery posts. I have no idea why it wasn't charging yesterday. Maybe removing F30 and reinserting it cleaned the pins. I hope my aux battery holds a charge now, it wouldn't be that difficult to add a charging cable snaked out from under the cabin filter cover to allow easy hookup to a float charger. And after running the engine for 30 minutes this morning the RED Visit Workshop is off!, it didn't have any additional messages to clue me in.
Update: The 12v Battery Tender from Costco has a short fused charge cable with ring terminals that works perfectly for maintaining the aux battery. I don't drive this car during the winter months because I live in the salt belt.
Update: The 12v Battery Tender from Costco has a short fused charge cable with ring terminals that works perfectly for maintaining the aux battery. I don't drive this car during the winter months because I live in the salt belt.
Last edited by ot1; Feb 17, 2017 at 04:06 PM. Reason: Update
Thread Starter
Super Member
Joined: Apr 2007
Posts: 633
Likes: 48
From: USA
2006 E320 CDI
Well my aux battery finally stopped charging properly, it drops to 11.75vdc immediately after turning off the engine. The vehicle monitors the aux battery and turned on a red visit workshop warning. When I pulled the battery to replace it with another Mercedes the date stamp said 22/09, 10 years out of that battery WOW! And i abused it by not charging it for nearly 2 years while in storage. Brought it back to life 2 years ago with a maintainer on it for a week.
Newbie
Joined: Apr 2022
Posts: 1
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2004 Merc w211
Cannot get rid of the red battery display on my 2004 W211. Both batteries have been replaced (main one was still pretty new . at
18 months) and the alternator is charging. Auxiliary bat reads 12.6v and main battery 12.7v.
Had a water problem in the trunk which is 90% fixed . Don't know if the two are connected as the water problem has seemingly been with me for a while. Is it possible to reset the display as both batteries are new and alternator is working fine.
18 months) and the alternator is charging. Auxiliary bat reads 12.6v and main battery 12.7v.
Had a water problem in the trunk which is 90% fixed . Don't know if the two are connected as the water problem has seemingly been with me for a while. Is it possible to reset the display as both batteries are new and alternator is working fine.
Member
Joined: Jun 2016
Posts: 128
Likes: 9
W211 E270 cdi 2004
Cannot get rid of the red battery display on my 2004 W211. Both batteries have been replaced (main one was still pretty new . at
18 months) and the alternator is charging. Auxiliary bat reads 12.6v and main battery 12.7v.
Had a water problem in the trunk which is 90% fixed . Don't know if the two are connected as the water problem has seemingly been with me for a while. Is it possible to reset the display as both batteries are new and alternator is working fine.
18 months) and the alternator is charging. Auxiliary bat reads 12.6v and main battery 12.7v.
Had a water problem in the trunk which is 90% fixed . Don't know if the two are connected as the water problem has seemingly been with me for a while. Is it possible to reset the display as both batteries are new and alternator is working fine.
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