03 E320 battery drain.
I put a new battery in and two weeks later same warning light came on. Checked voltage on battery and it was 11.4. Running it was 13.6 which seemed little weak. So I replaced Alternator. Two weeks later the battery was dead again. Alternator still reads 13.5 to 13.8. Mechanic said that's fine. Took the battery back and said it was junk so they replaced it under warranty. Drove it for two more weeks, came out in morning and battery is completely dead. Jumped it, drove it for half hour warning light turns off. But in the a.m it reads low 11 v. Something is draining the battery. I know there is that battery control module back their. Is this the culprit? How can I test this BCM
Oh I did test the auxiliary battery and it's 12.6 at all times. Man im tired of this car. 21 years old, I know I know. 😮💨 Thanks in advance



- Search on Youtube, there are quite some videos on this topic, especially for W211
- Seat control modules are a common culprit, you can test this by pulling out the fuses and checking the draw
- Alarm siren is a common issue, with age the onboard batteries will fail to hold charge. The alarm siren will keep requesting current from the car, preventing it from sleep and draining the battery
- Audio Gateway is a common issue
- Navigation unit can cause drain
- Voltage regulator can cause drain
- BCM can cause drain
- AUX battery can cause drain
- AUX battery relay can cause drain
- non-MB Original alternator can cause issues! There was a thread in W211 AMG section not too long ago if memory serves me right
I replaced my BCM (2005 CLS W219) with a BCM from a 2007 E-class W211. Also replaced the AUX relay, alarm siren, both batteries. I disconnected all Tele Aid/Phone capabilities and fiber looped out the components I dont need (you also need to code them out).
I can also highly recommend a bluetooth battery guard, it gives insight what is happening with the battery > https://mbworld.org/forums/c219/8443...ml#post8860681
- Search on Youtube, there are quite some videos on this topic, especially for W211
- Seat control modules are a common culprit, you can test this by pulling out the fuses and checking the draw
- Alarm siren is a common issue, with age the onboard batteries will fail to hold charge. The alarm siren will keep requesting current from the car, preventing it from sleep and draining the battery
- Audio Gateway is a common issue
- Navigation unit can cause drain
- Voltage regulator can cause drain
- BCM can cause drain
- AUX battery can cause drain
- AUX battery relay can cause drain
- non-MB Original alternator can cause issues! There was a thread in W211 AMG section not too long ago if memory serves me right
I replaced my BCM (2005 CLS W219) with a BCM from a 2007 E-class W211. Also replaced the AUX relay, alarm siren, both batteries. I disconnected all Tele Aid/Phone capabilities and fiber looped out the components I dont need (you also need to code them out).
I can also highly recommend a bluetooth battery guard, it gives insight what is happening with the battery > https://mbworld.org/forums/c219/8443...ml#post8860681



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- Search on Youtube, there are quite some videos on this topic, especially for W211
- Seat control modules are a common culprit, you can test this by pulling out the fuses and checking the draw
- Alarm siren is a common issue, with age the onboard batteries will fail to hold charge. The alarm siren will keep requesting current from the car, preventing it from sleep and draining the battery
- Audio Gateway is a common issue
- Navigation unit can cause drain
- Voltage regulator can cause drain
- BCM can cause drain
- AUX battery can cause drain
- AUX battery relay can cause drain
- non-MB Original alternator can cause issues! There was a thread in W211 AMG section not too long ago if memory serves me right
I replaced my BCM (2005 CLS W219) with a BCM from a 2007 E-class W211. Also replaced the AUX relay, alarm siren, both batteries. I disconnected all Tele Aid/Phone capabilities and fiber looped out the components I dont need (you also need to code them out).
I can also highly recommend a bluetooth battery guard, it gives insight what is happening with the battery > https://mbworld.org/forums/c219/8443...ml#post8860681
- Search on Youtube, there are quite some videos on this topic, especially for W211
- Seat control modules are a common culprit, you can test this by pulling out the fuses and checking the draw
- Alarm siren is a common issue, with age the onboard batteries will fail to hold charge. The alarm siren will keep requesting current from the car, preventing it from sleep and draining the battery
- Audio Gateway is a common issue
- Navigation unit can cause drain
- Voltage regulator can cause drain
- BCM can cause drain
- AUX battery can cause drain
- AUX battery relay can cause drain
- non-MB Original alternator can cause issues! There was a thread in W211 AMG section not too long ago if memory serves me right
I replaced my BCM (2005 CLS W219) with a BCM from a 2007 E-class W211. Also replaced the AUX relay, alarm siren, both batteries. I disconnected all Tele Aid/Phone capabilities and fiber looped out the components I dont need (you also need to code them out).
I can also highly recommend a bluetooth battery guard, it gives insight what is happening with the battery > https://mbworld.org/forums/c219/8443...ml#post8860681



