Technical Questions and Answers
Richard Simonds
Electronic issues
Q: I completed replacement of the last owner’s aftermarket radio and put back the original Becker radio over the course of the winter. As you might suspect, that involved rewiring speakers, reactivating the Bose system, etc. I disconnected the battery for the duration; upon reconnection I had learned things like how to reset the windows’ positions. I still am plagued with two problems I can’t find any information about. The first is that the seatbelt warning buzzer will not stop until it times out and the light for the seatbelt warning stays on. The second problem occurs when I start the car: The passenger seat returns to a position automatically (forward about two-thirds of the way and the back tilts straight up). Several hours of reading and researching have produced no clue where to start. From the schematic, it does look like the N2/4 relay can be the source of the problem. Do you have any suggestions?
A: This situation will likely require a visit to your dealer or an independent mechanic who subscribes to the Mercedes-Benz STAR Diagnostic System. So many components on our cars can only be programmed using this system; your problem isn’t something a user can fix without it.
Q: I have a 2008 CL63 AMG. Can the Mercedes-Benz software on that car support or link to the latest iPhones? (from the MBCA.org Technical Forum)
A: Changes in technology and interfaces between what is hard-wired in our cars and the software in the latest smartphones are definitely a challenge. Your dealer can check if Bluetooth connectivity is still working or can check to see if an update will allow your vehicle to connect to the latest iPhones. I’m guessing that it won’t be possible. If that is indeed the case, your only choices are to use an older phone, use your current phone unconnected or buy a new car – an expensive option just to use a phone.
Coincidental events
Q: I have a 2009 SL550 Silver Arrow edition, acquired last summer from a friend who had purchased it new. The car now has 22,500 miles on the odometer. My local Mercedes-Benz dealer replaced the trunk battery last week. Perhaps it is my imagination, but the transmission now seems to have a high-pitch spinning sound. Could this be related to the battery replacement?
A: My technical specialist conferred with mechanics from several Mercedes-Benz dealerships: All agreed that this is an instance where two completely unrelated events occurred at the same time. None of them knows of any correlation between the two circumstances. However, they all recommend that you don’t ignore the unusual sound; as this involves the drive train, you should have a technician listen for the sound you are hearing. Many dealerships and repair shops now have microphone-sensors they can use to help isolate the location of a noise – this is very useful as sound can travel along body and frame and seem to come from a place other than where it originates.
Follow-up: Thank you for the quick reply. I will continue to listen for the sound that does not seem normal to me. I wear hearing aids, so I’ll ask my wife – who does have good hearing – for her opinion. If she agrees there is an unusual sound, I will take the SL to my Mercedes-Benz dealer for a diagnostic test.
Battery questions
Q: I have a 1987 560SEC, chassis No. 126.045, manufactured November 1986. What is the normal parasitic draw on the battery when the car is parked and switched off? How long can the battery last before it won’t start the car, and before it has to be replaced?
A: I have polled several technicians, who offer this combined response: Battery draw at rest on older cars with limited electronic accessories is approximately 30-40 milliamps. That’s not enough to worry about if the car is driven monthly for at least half an hour. However, if the vehicle sits for more than a few months at a time, that is enough to partially drain the battery enough that it won’t start the car. That also decreases its life.
On a car built within the last 10 to 15 years, because there are more accessories that continue to draw power to maintain memories, in just a month or two the battery may drain beyond the point where it can start the car. If the car is going to be parked for more than a few weeks, it’s always a good idea to connect the battery to a modern battery tender that meters electricity to the battery as needed.
Q: I recently purchased a 1997 SL320. The battery in the trunk was 8 years old, installed back in 2008 by a Mercedes-Benz dealer using a genuine Mercedes-Benz battery. When I removed this 8-year-old battery, I found a brand new vent tube packet that was never opened; the battery’s vent tube was never installed. I wanted to connect a new battery to the vent hole properly but – and upon closer inspection – could not find a vent hole in the car. Have you heard of this? Apparently, the battery just vented into the trunk during the past eight years. Any advice would be helpful.
A: Based upon personal experience and double-checking with our Mercedes-Benz dealer and technical specialist, the battery compartment in the trunk should have a small rubber grommet to accept the vent tube from a Mercedes-Benz battery. You might require a good flashlight to see it.
As a point of information, most after-market batteries don’t have a vent; it is not necessary to vent the battery to the outside of the battery compartment, though for whatever sulfuric acid fumes might be present, Mercedes-Benz considered ventilation to be a good idea. It is your choice. Also, many newer after-market batteries are sealed, so venting is not needed; after-market batteries have no place to attach a vent tube to the battery.
Production sequence and VIN
Q: I have a question about the SL production table you show in “Evolution of the SL Class” (July-Aug. 2016 p. 61). The VIN number of my SL500 is WDBFA68F4YF190606, indicating that it’s an R129.068 model year 2000 produced in Bremen with production sequence number 90,606. However, you show that only 23,704 units of the 129.068 were produced from 1997-2001. How can it be that my production sequence number is nearly four times the total number of units produced?
A: Mercedes-Benz production sequence numbers are used for a continuing run of a specific model and engine, not for each of the sub-models of that chassis number. According to Daimler Archives, there were actually 204,920 R129s produced. 500SLs began production in 1989 and it is likely that a new production sequence would have been started to distinguish that model from the other R129 SLs (300SL, SL280 and SL320) produced at the same time. As shown in the production table, 70,344 500SL/SL500s were built with the M119 engine (129.066 and 129.067), and then, continuing the sequence, another 23,704 SL500s were made with the M113 engine (129.068). So your sequence number makes sense, being about 4,000 units before the end of SL500 production in 2001.