I am struggling with a red battery light issue on my 2009 W204 C63 AMG.
Background: I went to a local shop to get help in installing my long tube headers. To install LTH, we had to remove the alternator and one of the engine mount. Anyways, after installing the LTH while driving home I got red battery light, also an error for Auto Lamp Function Inoperative and luckily without further hassle I reached home. Later after two or three trips, I got battery light again and BTW continue to get Auto Lamp Function Inoperative light one each trip. So on that third trip the battery light came on and I went into limp in, car cut all the electrical like ABS, EPS and Radio. I barely reached home.
So I went to the local MB guy to check stuff on the car. He used STAR diagnostic equipment to check the whole electrical system. I even asked hi to check belt tension as we removed alternator. So after checking with STAR both battery and alternator are looking good. Can you guys suggest what shall I do next.
There's another piece that can go bad related to the alternator. I am blanking on what it's called, but maybe someone else can chime in.
Its called the voltage regulator. Funny thing is that the STAR diagnostics tool from MB tells that the Alternator and battery are both good so I am assuming the voltage regulator is good as well.
The alternator may be on it's way out if it's not a bad voltage regulator. I just had to replace mine at 117,000km. The bearings in the alternator had gone bad and it was making a somewhat loud whine. Same display message and symptoms as you. I just made it to my workshop when the car was so low on battery that the instrument cluster stopped working
The alternator may be on it's way out if it's not a bad voltage regulator. I just had to replace mine at 117,000km. The bearings in the alternator had gone bad and it was making a somewhat loud whine. Same display message and symptoms as you. I just made it to my workshop when the car was so low on battery that the instrument cluster stopped working
Did you car throw any codes? I used MB STAR diagnostic check the alternator and it came out good. Did you also get a alternator test out?
Think methodically. This happened right after major work in the engine compartment. Your failure is logically connected to that work. Examine everything that was removed/replaced and you will probably find your problem. I will guess a loose ground connection at the alternator.
A normal operating alternator, at idle will read UB/Voltage as 14.xx very fast and IB/current as over 10 amps when engine just started.
When engine running, if voltage lower than 12.7V and current showing minus sign, that means your alternator is not charging.
The red battery light icon, usually means battery not being charged by alternator.
This method is a way to test without using stand alone voltage meter and current clamp.
While engine is running, in NEUTRAL, throttle up the engine a few times to create a shake, see if whatever loose connection can be triggered , you will see voltage drop below 12.7 and current with a minus sign if whatever loose connection occurs again.
Try the dashboard voltage/current menu and let me know what are the numbers.
A normal operating alternator, at idle will read UB/Voltage as 14.xx very fast and IB/current as over 10 amps when engine just started.
When engine running, if voltage lower than 12.7V and current showing minus sign, that means your alternator is not charging.
The red battery light icon, usually means battery not being charged by alternator.
This method is a way to test without using stand alone voltage meter and current clamp.
While engine is running, in NEUTRAL, throttle up the engine a few times to create a shake, see if whatever loose connection can be triggered , you will see voltage drop below 12.7 and current with a minus sign if whatever loose connection occurs again.
Try the dashboard voltage/current menu and let me know what are the numbers.
Good luck
Thanks I will check as you told. I was trusting MB star too results when it says alternator and battery is good. I think I should also check your way.
check the battery terminals - possibly damaged the sensor on the ground cable? Lots to go wrong. So you took it to your MB guy and he tested stuff said alternator and battery are good but offered no solution or further diagnosis? Sounds like a clown. It has fault codes if those messages are popping up in the cluster. The auto headlamps is likely from the rain/light sensor. Have you had a windshield replaced or maybe get a rock chip in the top center area?
A normal operating alternator, at idle will read UB/Voltage as 14.xx very fast and IB/current as over 10 amps when engine just started.
When engine running, if voltage lower than 12.7V and current showing minus sign, that means your alternator is not charging.
The red battery light icon, usually means battery not being charged by alternator.
This method is a way to test without using stand alone voltage meter and current clamp.
While engine is running, in NEUTRAL, throttle up the engine a few times to create a shake, see if whatever loose connection can be triggered , you will see voltage drop below 12.7 and current with a minus sign if whatever loose connection occurs again.
Try the dashboard voltage/current menu and let me know what are the numbers.
Good luck
I have negative current and low voltage in neutral but good UB/IB in reverse, anyone know what my issue is?
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