Cristian Kruger

Hello.
My name is Cristian , i am from Romania and I own a C180 Sport Coupe 2001 with 210.000km.
A few days ago "undervoltage consumer defective" was shown on my display.
The deffective part that was responsable for this, voltage regulator. The component was changed. Everything was ok 14.28 and on load 13.81.
But , after a few minutes Battery/ Alternator visit workshop error appeared.
I went to an electrical specialist and everything seems to be ok. Battery status - very good, alternator status - very good.
Went to another workshop, and the same. Everything is normal. works well as it shoud but error is still there.
Any advice will be highly appreciated.
Thank you
PS.
Excuse poor language.

Glyn M Ruck

If the alternator is charging & the regulator cuts in at 14.2 volts & the battery passes a load test I would check all connections, earth straps etc.

Then try driving the car for a few hundred Km's & see if the warning goes away.

sinape62

Check your battery voltage before you start the car. Record it. Then start the car. Wait 5 or 10 minutes and wait for the battery to trickle charge, as it should be doing by the voltage Regulator via the reverse current relay. After the 5-10 minute wait, Put a volt meter on the battery when the car is running, then have someone press the gas pedal and look it the voltage drops on the battery. You shouldn't have a volt or amp draw, if you do the volt regulator can be the problem. As the battery should not be a electrical source after the car is started. If you have battery draw iT could be your alternator too. You have 210,000 KM, do you know if the alternator was changed? Alternator Brushes get worn or old springs, or bearings go bad.

Here's some basic info on electrical system: http://www.madelectrical.com/electri...witworks.shtml

Cristian Kruger

Hello and thx for quick answer. Here's how the things are. This morning i started the car. Battery was 12.76 V before starting. And after start 14.28 (since the motor was cold and idleing at 1200 rpm fow a short while). Everything was normal for a 20 min trip until i reach the destination and turned off the engine. When i started again after 5 min brake, the "Battery / Alternator " error was there after a few seconds. The wierd thing that i noticed, was the low beam (on auto position and headlamp mode on constant) doesn't work. No low beam on auto. Only on manual mode (if i turn the switch). I also covered the light sensor from the windshied an nothing happened. The lights wont turn on. Before leaving home the lights worked well (i have a garage and the lights turn on when the car is started).
@sinape62 : The alternator was removed from the car, when the voltage regulator was changed, and tested. It is in perfect working condition.

Cristian Kruger

Another measure set today after a 120km trip.
Al consumers on(short and long beam, heather, demisting, hazard lights, seat heather, etc) 13.67 at idleing and 13.87 at 2500 -3000 rpm.
All consumers off: 14.28 idleing and 14.45 at 2500 - 3000 rpm.
When the night came, only daskboard lights went on and the parking lights (position lights) when light switch on AUTO. On manual mode low beam works as it shoud.

VVF

I'd say something wrong with voltage regulator...
Should be around 13.6 idling with no consumers, 14.x at 2k RPM.

Or the alternator is dying, but afaik the brushes and stuff are all inside the VR, so I'm not sure what could fail inside the alt itself.

Glyn M Ruck

These cars are fitted with two alternator types that talk differently to the electronics.

Make absolutely sure that the correct VR was fitted.

Get the car onto a Star to check for Canbus faults etc.

These cars are VERY voltage fussy. Have your battery properly load tested.

Cristian Kruger

This is the second time when it happens. Like yestarday morning , today, i started the car and no faults. I had a 60 km trip without any problems. The error appeared when i started the car again.
Exactly like yesterday. So when i leave the car over night (or for a long period of time), there is no error at the first start.
Only at a second start the problem appear.
I went today to another garage and have the car tested for alternator and battery. They are in perfect working condition.
I'll go and have a star diagnonse and see the result.
The VR is brand new, made by BOSCH like the one i have replaced. The only difference was Benz logo
Could be a faulty SAM module ?
Like it happened yesterday the light sensor stopped working when error appeared.

sinape62

Interested in the findings... Keep us posted.

Cristian Kruger

Today i managed to establish a pattern.
First start is normal with no errors, usualy in the morning of if i'm not usung the car for a least 6 - 8 hrs.
After that the error keeps apearing. Or "Battery/Alternator" or Consumer defective. One of them or both. There is no pattern here.
When the errors are present the light sensor is semifunctional. Only the dash and parking lights are turning on. If the errors are not present the low beam is working too.
This is the car behaviour after replacing thr VR.

Holmes5518

You have the wrong voltage regulator.

W203coupe

I had this on my c180 this kept on coming up every time I started the car up. Turned out in the end that it was. A loose bolt where the wires go onto the battery and couldn't charge it properly. I expect as I drive over potholes and bumps must loosen the screws after a period of time.

Cristian Kruger

Hello. I ordered a new VR, this time from dealer (payed 3 times the price...). I will pick it up today and put it on the car. I'll keep u posted.

Cristian Kruger

After replacement with the original part(VR), everything is working as it should. Thank you very much for your help.
Cristian

Glyn M Ruck

Pleased it's sorted. Correct VR is critical for interface with the electronics.

Cristian Kruger

Actually there are 3 types. 80,100 and 120 amp alternators. Usually most cars have the 100 type. Because of my sunroof mine is equiped with 120. The first VR was for 100 model and because of that, all the troubles...

Glyn M Ruck

It's actually got nothing to do with the amperage but that needs consideration too.

It has to do with comms.

VR's must always be ordered against your VIN. As must alternators

Glyn M Ruck

Here is the explanation.

"Alternators are not what they used to be, the difference is in the voltage regulators.
There are 3 variants:

MFR (multi function regulators)
LIN (local interconnect bus)
BSS (bit synchronous bus)

BSS and LIN are used depending on the engine ECU type
either ME2.8 or SIM4, these regulators actually communicate with the engine ecu and transfer infomation between each other, the engine ecu has control over the alternator to be able to control the torque loading for emissions requirments.
So you cannot swap an alternator with a BSS regulator with one with say a LIN bus. no communication will take place"

Cristian Kruger

Very useful information. Soon we gonna need an engineer to have a flat tyre replaced

jetoni

I have the same problem my service saw to change modul for relays what do you think bater and alternator are good please help

Simon Holmqvist

Hi i think i have the same problem as Cristian but, I just want to check that my vr i correct with my vin. Just bought the car and looks like itīs an replaced generator. So i donīt know if the generator came with the wrong vr. How do i confirm i have the right vr for my car?


Glyn M Ruck