W211 E270 Voltage is unstable
Thread Starter
Junior Member
Joined: Dec 2018
Posts: 26
Likes: 0
w211
W211 E270 Voltage is unstable
Hello MB drivers. I have an issue with my car. The thing is that it starts fine, no error codes whatsoever. When i put the key in and i navigate to Voltage Controls on dashboard i see 12,1V. When ignition is on 2nd turn it shows 11,7. On starting it drops to 10,9. After start it shows 11,5 and slooowly going up, on indle with no consumers, shows 13,2 max. If i give it a little bit of gas it jumps to 13,9v
But when i load all the electric consumers, on idle it drops to 11,5 on the display and at the battery terminals.
Things that i did.
1. Changed alternator relay with brushes. No results.
2. Cleaned all the terminals. No results.
Any advice? Save me from this misery guys
But when i load all the electric consumers, on idle it drops to 11,5 on the display and at the battery terminals.
Things that i did.
1. Changed alternator relay with brushes. No results.
2. Cleaned all the terminals. No results.
Any advice? Save me from this misery guys
MBWorld Fanatic!
Joined: Feb 2014
Posts: 6,190
Likes: 1,549
From: MA
2008 E350 4Matic, 2011 E350 4matic
There's nothing wrong, it's like that at idle. Alternator generates power from the belt which comes off the engine. At low idle, it doesn't generate enough power to power everything. When you're driving, the voltage should go up to around 14.5.
Thread Starter
Junior Member
Joined: Dec 2018
Posts: 26
Likes: 0
w211
Ahh. I see. But still when i am driving and turning on rear and fron window defrost, also heated seats and steering wheel. I get 12,3v max when driving. Maybe alternator is bad? But still i have no errors displayed on display.
MBWorld Fanatic!
Joined: Feb 2014
Posts: 6,190
Likes: 1,549
From: MA
2008 E350 4Matic, 2011 E350 4matic
You have too high a load on it. It's still fine. You only get a warning when the voltage drops below 11 volts. Voltage regulator could be bad, but that's on the alternator. In the US, the auto parts store will do a load test and also check the charging system for free. Not sure what country you're in, but you could have them checked. If the alternator was bad, it wouldn't go up to 13.9. I think you just have too much on, what's the voltage when all that is off?
Thread Starter
Junior Member
Joined: Dec 2018
Posts: 26
Likes: 0
w211
You have too high a load on it. It's still fine. You only get a warning when the voltage drops below 11 volts. Voltage regulator could be bad, but that's on the alternator. In the US, the auto parts store will do a load test and also check the charging system for free. Not sure what country you're in, but you could have them checked. If the alternator was bad, it wouldn't go up to 13.9. I think you just have too much on, what's the voltage when all that is off?
