Testing alternator or other component in the charging system

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?

Fortunately, I have access to a Star diagnostic and I will run the test you suggested tomorrow.

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?

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.

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.

I will check when I arrive home tonight. Thank you for the suggestion.

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

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.

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.

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.

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.