Testing alternator or other component in the charging system

Tiny
KEVIN HENNELLY
  • MEMBER
  • 2005 MERCEDES BENZ C230
  • 1.8L
  • 4 CYL
  • 2WD
  • MANUAL
  • 155,000 MILES
I dropped a wrench while making a repair. It struck the alternator power connection and the frame causing a short circuit. When I started the car, the battery/alternator warning light illuminated. I checked the voltage with the car running and it is either 12 or 12.1 volts, so the system is definitely not charging.

I am trying to determine whether the alternator was damaged by incident or if some other component of the system is causing the problem. I used a voltmeter to perform a diode test and it appears that the diodes were damaged. This is the first time I have worked with a potentially damaged alternator and I am unsure of my testing skills and techniques. I tried to have the alternator tested at two auto parts stores, but the alternator did not fit on their machines correctly and they couldn't run the test.

I purchased a used alternator from a recycler and replaced the voltage regulator on it. It passed the diode test that the original alternator failed. Are there any other tests that I can run on the used alternator before installing it in the car? I will try some other parts stores to see if they can test the alternator, but the machines I've seen appear similar and I am not sure I will be able to find someone to test it.
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Friday, June 12th, 2020 AT 7:54 AM

37 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

It sounds like the alternator regulator was damage especially if the diodes are bad. It will need replaced. Even if you get it to charge, the diodes will allow a constant draw on the battery likely draining it overnight.

Here is a link that explains in general how to replace one:

https://www.2carpros.com/articles/how-to-replace-an-alternator

Here is a test for diagnostics. The attached pics indicate directions.

2005 Mercedes Benz C 230 (203.040) L4-1.8L SC (271.948)
AR15.40-P-5000P Test Alternator and Regulator
Vehicle Starting and Charging Charging System Voltage Regulator Testing and Inspection Component Tests and General Diagnostics AR15.40-P-5000P Test Alternator and Regulator
AR15.40-P-5000P TEST ALTERNATOR AND REGULATOR
AR15.40-P-5000P Test alternator and regulator

Component Identification
Pic 1
Steps 1-4
pic 2

Commercially available tools
pic 3

__________________________

Let me know if I can help.

Joe
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Friday, June 12th, 2020 AT 10:40 AM
Tiny
KEVIN HENNELLY2
  • MEMBER
Thanks for the reply. You posted a YouTube video showing how to replace the alternator on a C230 and it was extremely helpful. I removed the original alternator that I thought I damaged with the wrench and took it for a test. The person who ran the test said it was a good alternator, but I don't have any specific data. With the alternator disconnected from the car, the diode test provided a different result. Now, I'm not sure the problem is the alternator itself. Could I have damaged some wiring or another component?
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Friday, June 12th, 2020 AT 4:37 PM
Tiny
KEVIN HENNELLY2
  • MEMBER
Fortunately, I have access to a Star diagnostic and I will run the test you suggested tomorrow.
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Friday, June 12th, 2020 AT 4:38 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

Anything is possible. I attached a picture of the wiring schematic for the charging system. Since the starter is working, I assume the starter/alternator fuse (175 amp) is okay, but check it anyway.

Also, there should be a black wire at the alternator. Check to make sure it is getting power.

Let me know.

Joe
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Friday, June 12th, 2020 AT 11:24 PM
Tiny
KEVIN HENNELLY2
  • MEMBER
The diagram is helpful. I ran a scan with the STAR tool and the system returned code 2062-002 - Alternator serial interface. No connection to the control module
N3/10 (ME-SFI [ME] control unit)

Based on your diagram, this seems to suggest that there was:

1. Damage to the blue wire that attaches to the control module.
2. (Worse case scenario) a damaged control module.
3. Damaged connector to the alternator.
4. Damaged voltage regulator on the alternator itself since this attaches to the blue wire.

Do you think I am on the right track?
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Saturday, June 13th, 2020 AT 9:33 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Yes, it sounds like you are on the right track. With this code, it is usually the regulator unless the wire was damaged between the ME-SFI control module and the alternator. Was there any damage to the wires when you were working on it? Also, since you are getting the code, I don't think it's the control module. I suspect it's the regulator or the blue wire you referred to was disconnected or broken somehow.

Let me know.

Joe
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Saturday, June 13th, 2020 AT 7:22 PM
Tiny
KEVIN HENNELLY2
  • MEMBER
Thanks. It is good to hear that damage to the control module is a less-likely scenario. I couldn't see any damage to the connector or the wires. I'm planning to buy a new voltage regulator and see whether that fixes the problem.

In initially thought it was the voltage regulator. I removed the alternator from the car and had it tested. The test showed it was okay, but I've since found several resources that suggest that the bench test cannot detect issues that are vehicle specific such as communication between the control module and voltage regulator. I don't like to "throw parts at a problem" and a Bosch voltage regulator is $74.00. However, I think I have enough information to justify making the investment and seeing if that works. I'll update the post after I install the new voltage regulator.

I appreciate your time and expertise.
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Sunday, June 14th, 2020 AT 8:06 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Here are the directions for replacing the regulator. The attached pic correlates with the directions.

____________________________________

2005 Mercedes Benz C 230 (203.040) L4-1.8L SC (271.948)
AR15.40-P-5760P Remove/Install Regulator of Alternator
Vehicle Starting and Charging Charging System Voltage Regulator Service and Repair Procedures AR15.40-P-5760P Remove/Install Regulator of Alternator
AR15.40-P-5760P REMOVE/INSTALL REGULATOR OF ALTERNATOR
Remove/Install Regulator Of Generator

pic 1

DANGER:
1. Lethal injuries are possible if vehicle slips off of lifting platform
- Align vehicle between the columns of the lifting platform and position the four support plates at the lifting platform support points specified by the vehicle manufacturer.

2. Risk of explosion from explosive gas. Risk of poisoning and caustic burns from swallowing battery electrolyte. Risk of injury through burns to skin and eyes from battery acid or when handling damaged lead-acid batteries
- No fire, sparks, naked flames or smoking.
- Wear acid-resistant gloves, clothing and goggles. Pour battery electrolyte only into suitable and appropriately marked containers.

1 Disconnect ground cable of battery
2 Remove generator (G2)
3 Unscrew collared nut (2)
4 Unscrew nut (3)
5 Unscrew cover bolt (4)
6 Remove cover (1)
7 Unscrew bolts (6) of regulator (6)
8 Remove regulator (5) towards the side

NOTE: Installation: Do not damage carbon brushes

9 Install in the reverse order

__________________________________________

I hope this helps.

Take care,
Joe
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Sunday, June 14th, 2020 AT 5:22 PM
Tiny
KEVIN HENNELLY2
  • MEMBER
I replaced the voltage regulator. Unfortunately that didn t resolve the issue.

I took a second look at the connector and the blue wire and I could not see any damage. I cannot see more than a few inches of the blue wire and I cannot rule out that is damaged in a spot I cannot see. Another potential problem is that some other component in the alternator is damaged and the test equipment at the auto parts store is not detecting it.

I would be willing to replace the entire alternator if I am able to rule out all other potential sources for the problem.
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Thursday, June 18th, 2020 AT 8:59 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Kevin,

Mercedes is very secretive with info, so the only way I can provide specific test is to know if there is a diagnostic trouble code present.

Is there anyway for you to check right at the alternator for output rather than doing it at the battery?

Joe
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Thursday, June 18th, 2020 AT 9:15 PM
Tiny
KEVIN HENNELLY2
  • MEMBER
I will check when I arrive home tonight. Thank you for the suggestion.
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Friday, June 19th, 2020 AT 4:05 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Sounds like a plan. Let me know what you find.

Joe
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Friday, June 19th, 2020 AT 8:49 AM
Tiny
KEVIN HENNELLY2
  • MEMBER
I am planning to attach one wire to the alternator and a second to the negative battery terminal. I will attach both of these wires to my multi-meter. Will that yield the reading I need?
Thanks
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Friday, June 19th, 2020 AT 9:31 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
As long as you attach to the output, yes. Actually, you should be able to attach right at the battery wire at the alternator.

Just be careful.

Joe
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Friday, June 19th, 2020 AT 6:14 PM
Tiny
KEVIN HENNELLY2
  • MEMBER
Thanks again for your reply. I checked the voltage at the alternator and it was negligible - approximately 0.4 volts. I connected the STAR system and it read the same fault code I posted previously - 2062-002 - Alternator serial interface. No connection to the control module. When I ran the STAR system, there were menu choices for alternator testing, but they would not run on my system. (I bought the system used and I don't know much about its origins. It may be a Chinese clone.) I've posted a video showing what happens when I attempt to use the alternator diagnosis menu. If you pause it at about the half-way point you should see a message that says, "DAS and WIS are active at the same time. It is possible to switch over between the systems with the key combinations ALT + TAB." I'm not sure whether doing that will allow the test to run, but I will give it a try later.

I've also posted photos showing the data connector and the battery connector to the alternator and the voltage regulator that I removed. I cannot see any visible damage.

I think the problems could be:

1. Damage to another part of the alternator.
2. Damage to the communication system between the ECU and the alternator which is preventing the alternator from receiving a signal to turn on.

I was thinking of buying this: https://www.harborfreight.com/Computer-Safe-Automotive-Logic-Probe-63597.html and using it to probe the connection from the ECU to the alternator. My thought process is that it will show whether there is a signal coming from the ECU.

If the alternator is indeed damaged, it appears that buying a rebuilt alternator is the best option. Before I do that I would like to rule out the other possible causes.
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Saturday, June 20th, 2020 AT 8:49 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
I watched the video. That jumps around really fast. After the 4th or 5th try, I got it paused so I could read it. LOL

Try what it is saying. The system seems to be glitching for some reason. As far as the start of this issue, I wouldn't think there is a break down in communication. I have a feeling it's the alternator itself, but testing will tell for sure.

Let me know.

Joe
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Saturday, June 20th, 2020 AT 9:14 PM
Tiny
KEVIN HENNELLY2
  • MEMBER
Thanks for the reply.

Unfortunately hitting alt and tab didn't do anything. I did find another menu (see photo) that suggested (1) checking the communication line between the alternator and the control unit for a break or short and (2) checking the regulator (assuming it means voltage regulator) with an oscilloscope. Because I replaced the voltage regulator (and I don't have an oscilloscope) I will try to figure out how to check the communication line.
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Sunday, June 21st, 2020 AT 8:30 AM
Tiny
KEVIN HENNELLY2
  • MEMBER
I used a test light to determine whether there was connectivity between in the data wire from the ECU to the alternator. It may be hard to see in the photos, but the LED in the test light is glowing red indicating it has power. I don't know whether it is sending the correct data to the alternator when the system is on, but I guess there are no breaks in the wire. I also cannot see any damage to the part of the wire that is visible or to the connector.

On a different but related topic, I'm wondering whether something wasn't installed on my STAR system. It does not have an icon for the WIS.
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Sunday, June 21st, 2020 AT 9:35 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
It looks like the communication is open so that wire isn't the cause. The last thing is the alternator. I suspect there must have been internal damaged done (somehow) to the alternator. Nothing else makes sense. Also, in your original post, you indicated you tried to have it tested at two different parts stores but it wouldn't fit their machine. Is that correct? Is there any reliable shops in the area that would test it for you? For example, a place that deals specifically with auto electrics?
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Sunday, June 21st, 2020 AT 8:50 PM
Tiny
KEVIN HENNELLY2
  • MEMBER
I first tried a specialist alternator/starter rebuild shop. He said that he didn t work on Bosch because he couldn t get parts. (He had piles of starters and alternators most of which appeared large enough to be from commercial vehicles). His test machine was in a dark corner of his shop. I didn t get a close look at it, but it appeared old and rudimentary. He said he thought the alternator was good, but he didn t provide any details regarding how he reached that conclusion.

I had also purchased a Valeo alternator from a recycler. I took that to two auto parts stores and they couldn t fit it on their test machines. I later brought the Valeo alternator to an Advance Auto store. That store had the correct adapter mechanism and belts and could test the Valeo alternator. The technician told me it was defective and I returned it for a refund.

I am planning to take the Bosch alternator to the Advance Auto with the functioning equipment and have it tested. Their equipment seems newer than the machine I saw at the specialist shop and it may provide more detailed information about the Bosch alternator.
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Sunday, June 21st, 2020 AT 9:45 PM

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