Investigation: Why serial numbers aren’t so informative

Earlier, an Instagram user commented on our post about Nonna (tagged as #Nonna144545): “I don’t know why people call the pre-facelift S 320”. His implication is that since it is a pre-facelift, it should be 300 SEL.

Depending on common sense, people will have different concepts about the information “144545”. For some people it may not mean anything, for others they can directly associate it with the correct name corresponding to this period, and for some people it may be vague. I can tell you that the third idea could be more advanced than the second one to some extent, and this is what we need to discuss today.

For automotive journalists or people who don’t care much about 140, they like to use simple “early” or “late” or calendar time to describe the time of 140 changes. For junior enthusiasts, they can accurately define the time of improvements to the model year. For some experts, they can use the last 6 digits of the VIN to limit the period of the modifications. So, are these enough?

Obviously, all these answers can be correct, because they come more or less directly or indirectly from Mercedes-Benz’s official language. Mercedes sometimes uses facelift to define the most significant changes of the 140, which is interpreted as “early” and “late”. In the North American market, where model years are important, Mercedes Benz of North America uses different model years to highlight all improvements, and model years are the main way to distinguish cars. As for the serial number, which experts prefer, it is obtained from Mercedes workshop information such as EPC or WIS, and they are considered the most accurate.

Of these three methods, the serial number is the fundamental basis, because the model year describes the set of serial number ranges, and the facelift is equivalent to the set of model year ranges. The serial number is currently the most accurate information provided directly by Mercedes, and it is considered to be like the Bible. However, we must emphasize here that it cannot be absolutely relied on, and for this reason I will give a few examples to highlight its weaknesses in several aspects.

Cognitive Deficit

Octavius, A149549 is my first car, a 140.057 with a delivery date of 2 August 1993. At first, I was unsure if it was a 600 SEL or an S 600, as both data sheet in the owner’s manual and the build sheet in the body described it as a 600 SEL, but the name plate on the trunk lid and the paperwork issued by the administration claimed S 600. Let’s skip our amateur guesses and go straight to Mercedes’ official information: the EPC states that cars before A151344 should have used the 600 SEL name plate, and Octavius ​​as A149549 falls within this range.

If you trusted Mercedes aftermarket as I did instead of lazy government employees and dodgy car importers, you would have thought, as I did, that when the car was registered 5 months after production the dealer installed a more fashionable name S 600 and the DMV happily accepted it without checking any factory material. For a while I did this, changing the name plate to 600 SEL for authenticity. To the average passerby, the pre-facelift 140.057 should also be read as 600 SEL.

But there is another image that lingers in my mind: I removed the S 600 name plate myself and have some photos before removal. The S 600 looks to be the factory position, and you have to know that if you have a 600 SEL, it is difficult to find the correct installation position of the S 600. Before the 140 appeared as a hobby, although it was not uncommon for the name update to be some kind of vanity project, I had never seen such an accurate position. Christian, the founder of mb-w140.de, his dad bought a used 1998 S 600 from Mercedes in 1999, and that car probably had the wrong S 600 position due to the polishing of Mercedes’ used car department. It was not even a normal S 600, but the official car of Klaus-Dieter Vöhringer, the member of the board and responsible for production, and even such a car was not treated professionally.

Later experience has proven that I was wrong, Octavius ​​is indeed an S 600. Many of the data sheets collected later have outdated old names, you can say that production has not fully kept up with the times. And the European V12 owner’s manual was not updated since August 1991 until 1994 facelift, even if you received a new S 600 in March 1994, the owner’s manual still says 600 SE / SEL. August 2 is a relatively safe date compared to cars produced in June and July 1993. If you check the production sequence, cars produced from June 1st onwards have started to use the new name plate.

The name plate is just the tip of the iceberg of Octavius’s vague identity. We don’t know the model year of Octavius. As a car produced in August 1993, is it model year 1993 or 1994? Before MY1996, there was no model year definition for European cars. You can only judge which model year it is by comparing the details on the car with cars with model years in the US and Japan. If it is just based on what Mercedes aftersales said, the range of the new name plate is consistent with the range of MY1994, so Octavius ​​should be MY1994.

But Octavius ​​has almost no features of MY1994. For example, it does not have a black plastic trunk auxiliary handle and no new radio. So there is overlap in the seemingly consistent parts range, and many parts have not been updated at the same time. It is MY1994 in name, but it is still MY1993 in technology. This is the so-called cognitive defect. If you say you have a 1993 S 600 in the North American market, it does not exist, but you can say so in Europe. Or prepare an explanation article like this in advance.

Repair Trap

Due to the wrong serial number range given by the EPC, if you enter the Octavius ​​VIN, the system will filter out the S 600 and only allow the 600 SEL to be ordered. So owners who can’t figure out the part number themselves will get the wrong name plate. The dealer will insist they are right, even if they are wrong.

As an August 1993 car this problem is not so obvious, because there is some safe distance from the name change in June 1993. Nonna, A144545 is the S 320 produced on June 3, 1993, the car questioned by the Instagram user. Not only was she produced on the third day of the introduction of the new name, she was also produced on the third day of the introduction of the new Motronic 104.994. On a car with the M104, the June 1993 change was quite drastic, resulting in a lot of technical differences.

Nonna faced the name plate problem earlier, as A144545, she is 6799 cars older than the EPC-defined A151344. But it is undeniably an S 320, and one of the first. If the name plate isn’t convincing enough, let’s look at it another way. All cars with the M104 were upgraded to Motronic in MY1994, not indifferently like the M120. Everything from the cylinder head to the electrical system was redesigned, and this alone can easily distinguish between a MY1993 with 104.990 and a MY1994 with 104.994.

The smart EPC can display the correct engine parts catalog based on the engine number in the data card, so even though A144545 is still in the range they claim to be 104.990, it is correct from Group 01 to Group 22. But the EPC is not so smart in the group after the transmission, and because the VIN is in the MY1993 range, the body is also identified as MY1993. The difference in the electrical system in Group 54 is catastrophic, and none of the engine-related wiring harness part numbers provided are applicable to 104.994. For the engine compartment wiring harness, as per their statement, A1405400833 is suitable for the following cars:
Up to ident. no.:
A 151632 EXCEPT FOR
A 147846,
CODE 804
ALSO INSTALLED IN VEHICLE FROM A 151633 WITH CODE 803
AUSTRALIA UP TO END OF MODELYEAR 93

Nonna as A144545 is definitely in this range, and as a stealth MY1994 it also does not have code 804. I just happened to find a good deal NOS to install, but I doubted if the statement was accurate as they screwed up so many times around MY1994. Until I found near the plug that connects to the engine wiring harness that the part number is actually A1405406932. So it is best to check the original part number to determine the correct number. For the starter and generator harness, unfortunately the small label with the part number is located on the wire of the oil level sensor, which rarely survives. You need to have some knowledge or practice to find the correct part number…

Another example of starter cable comes from an early facelift car I worked on, A199062, which came with SA code 856 (known as MY1995 in markets like North America and Japan, with SA code 805). When I entered the VIN of the A199062, EPC popped up something like this: I need A1405402730, which is for cars after A192209 or with code 856. A199062 is 6853 numbers after than A192209, which seemed like a safe interval, so since the EPC clearly stated that the cable changed with 856, I ordered the A1405402730 without investigating.

I already noticed the difference when I received the harness and started to disassemble the degraded original cables, later next to the oil level sender I found the label with part number A1405402630. According to the EPC, A1405402630 is only suitable for cars between A151633 and A192208, but it is clearly on A199602. The car has only traveled 9966 km and still has all original harnesses. The date on the label also tells that it was approved on 15.09.93, so obviously such cable were used at the beginning of that period, but not in March 1994 when the 856 started serial production.

Unfortunately, the closer you get to the change boundary, the less accurate the serial number is. It must be known that the 140 has countless small changes in production… so the danger is everywhere, even in North American and Japanese cars that seem to have a fairly clear model year. This is why it is better to check the number on the old part instead of ordering the new part directly from the EPC information. As I said, many parts have worn numbers after years of use, and they may not have been replaced correctly, so knowledge and luck are needed…

Why

The inaccuracy of using serial numbers to define intervals is beyond imagination, and perhaps no information based on them is absolutely accurate, even for the largest events such as facelifts. Endless examples could be given, and the following is just one. EPC claims that back-up aid is installed up to A255509. Note that this range is exclusive, meaning that cars after A255509 do not have back-up aid, and cars before A255509 have back-up aid. However, it is easy to find cars after this range that still have back-up aid, such as A259468 below, which is nearly 4,000 cars later than A25509.

The reason why I chose the back-up aid as an example is that it is not a trivial matter. The production preparation for this starts from the body-in-white, because two holes are reserved in the rear fender. Contrary to the clear boundaries claimed by the EPC, in fact, on adjacent serial number cars, you will see that the next car has no back-up aid, and the next car has a back-up aid.

A260734, without back-up aid.

A261130, with back-up aid.

In Investigation: Who’s the last 140?, we introduced the difference between VIN and production number, that is, the serial number of VIN does not represent the actual order of car production. VIN, as a number starting from the anti-theft function, only represents the identity of the car, and the serial number means the order in which this identity is created, not the order of production. There are many factors to consider in actual production, such as some cars of the same color will enter the paint line at the same time, but their VIN serial numbers are far apart.

Each car will have a build sheet left by the factory, and the production number is the most eye-catching information on that sheet. For a long time in the past, the production number could only be obtained through the build sheet. Since the release of the new EPC in 2018, the production number has been added to the data card. You can think of these numbers as more accurate as the serial number of the car production. However, the EPC has not yet used the production number as a reference for the range, and perhaps it will never be…So for some specific topics, you need a lot of experience and luck