Ed Clark

Hello all,


I have a C230 that had the usual type phantom alternator type issues. Then finally it took a dump. Voltage regulator went bad. I could see the voltage soar after starting the car to 16-17 volts until apparently the computer would get in involved and cut it off.


I removed and replaced the regulator. But still no charge on start up. So I blipped the throttle to just over 2400 and the alternator lights off and starts charging properly.


So I checked the wiring and couldn't find anything. Checked the alternator igniter voltage and got about 10-11 volts. That should normally be enough to start the alternator. But I still get a P0620 code.


I even tried starting the car with the throttle open to see if I could "trick" the computer. Nothing.


Since the alternator lights off at 2400 rpm this is almost unnoticeable and my wife has been driving it for almost 6 months now. But that darn light! Of course you can't just start it and let it idle without blipping the throttle over 2400. But driving the car and getting over 2400 rpm is nothing, not even for her.


Thinking maybe there was some sort of code stored that maybe giving me trouble, I bought a iCarSoft MBII scanner. Works great but that didn't help. But the scanner did say that the ignitor voltage was only 5 volts. Is this correct? If so it may not like 10-11 volts. At this point I'm thinking that the soaring voltage with the bad regulator may have taken something out in the monitoring circuits.


I've spent a lot time looking for others that have had this problem with no luck. Anybody seen this? Maybe a good schematic or theory of operation? How about some good old fashioned ideas?


Thank you,


Ed

Russell Ormerod

Hi,

Is it the genuine and correct voltage regulator for your car?

Ed Clark

"Correct one?" Should be.


https://www.ecstuning.com/b-valeo-pa...031544006~val/


"Genuine?" Probably not. I considered the regulator again... simply because there was 10-11 volts on the ignitor wire. But once I saw that it wanted 5v and it was nowhere near 5 volts... I started to wonder if.....


So obviously, your going to suggest a GENUINE MB regulator. :-)


Thank you,


Ed

Russell Ormerod

If the charge lamp only goes out over 2500 RPM. Maybe have a look at the rectifier. Also check the rotor winding should be around 3 to 4 ohm I think.
Maybe be easier to replace alternator than buy a Valeo regulator from mb.

Ed Clark

The light never goes off. It's only off for about 5 seconds after starting the car. I did check the rectifiers while it was out. I'm an electronics type. :-) Which is why this is annoying me. I have found Valeo regulators for a reasonable prices... if they really are... I'll probably hold my nose and buy another one because I do concur that regulator is probably bad. My guess is that the ignitor voltage is getting to the regulator but it's not doing it's job.


I've been in there enough now that I think I can change the regulator without actually removing the entire alternator this time.


I'll check back with results for the archives when I get it sorted out.


Thank you again for your replies!


Ed

junkyarddawg

Your car (2003 C230K, M271) has an alternator that is controlled by the SIM4 engine control module via a LIN comm bus. The engine control module also sends terminal 61, "alternator rotation" information, to the LF sam/fuse relay module via the BSS data interface, which is conditioned by LF sam then sent to the instrument cluster via the CAN-B data bus. The alternator can operate in default modes when the LIN bus is compromised but fault codes should be stored in the engine module, if the BSS line is compromised the LF sam will not receive the terminal 61 signal, and there could be no codes stored in the engine control module, but the instrument cluster will be unhappy resulting in Batt light and possibly "Visit Workshop" message. The same condition could occur if the LF sam failed to "condition" or send the correct "CAN" message. This type of fault could be internal to the LF sam or caused by CAN comm faults, in the latter case you should see CAN fault codes.
or, Maybe its just a bad alternator? Good used parts can be found at LKQ
I tried to make it as simple as possible, but because its a Mercedes Benz, they did not.
Divide and conquer

Ed Clark

Sorry, I don't recall getting a notification for your reply. I appreciate your efforts and input.


But, I finally got a new regulator in the mail and time/weather to put it in.


The car is fixed now. The first replacement regulator was in fact a Valeo. But one tiny difference that I didn't notice the first time putting it in. The first Valeo replacement, the one that didn't work has two contacts in the exciter connector. The new Valeo replacement only has one. That's pretty much the only difference between the two regulators. Based on the results I'm gonna guess that makes a big difference. Used a scan tool to clear all of the codes and the car again runs fine.


I'm gonna guess that the second pin in that connector is the ground or return for the exciter line. But at this point, I don't care much! :-)


We really like the car and how it drives. But it is a maintenance nightmare. There is always something electrical broken and needing repair. At least getting the alternator in and out is much easier to get out once you've done it a few times! Still harder than many other makes.


Now I just have to fix the turn indicators, the dimming dash display, the sun roof, the tailgate open sensor and leaking windshield washer tank.


Thanks again all!


Ed

Ed Clark

One last follow up.


Last night I checked the first replacement against the original regulator, the original OEM regulator.


The first replacement was exactly the same regulator as the original. It is a Valeo and almost exact down to every casting and every location of print. Both have two terminal contacts in the exciter connector.


This leads me to believe that the first replacement regulator was in fact the correct one and most likely defective right out of box.


Since the single contact regulator is now working perfectly, that also tells me that the number of pins in the exciter connector probably doesn't mean anything and that it's most likely a parallel ground.


Just putting a period on this for others that may find this thread during a search. I've noticed that there are many threads with interesting issues, but the OP never ends them by stating what actually fixed the problem. That makes the entire thread almost worthless as archived data.


Thank you,


Ed Clark