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The turn signal in my driver's side headlight isn't working. I initially thought it was a problem with the wire insulation in the headlight because the insulation in my passenger side headlight had disintegrated. When I removed my headlight, I found that the wiring was pristine.
After a bit of head scratching and 30 minutes of searching, I found a good write up about the problem on the SL forum: Turn Signal Repair
There are some posts about this issue on the W203 forum, but I think the one on the SL forum is well illustrated and clear.
Btw, GM has had similar problems for a long time.
However, the replacement sockets are not NOS (New Old Stock), they are new from a cheap POS outsourced vendor (like most of GM's older replacement parts!). Those sockets last ~3-9 months.
The "Help Section" replacement sockets are about the same.
Ironically, a cheap China-clone fully stocked headlight assembly can be bought for ~$70. It doesn't take even 5mins to replace on many older GM - and no tools required. And, those have lasted over 5 years.
Interesting information about the GM headlights. At one time all U. S. vehicles were required to use identical DOT-approved round headlights. On the one hand, that made it easy to find replacements and reduced the number of potential failure modes. On the other hand, it limited design options and if the U.S. maintained that requirement innovations like HID and LED may have come more slowly or not at all.
Returning to the subject of this thread - I found a post on BenzWorld that provides more detail on the installing the replacement socket: Installation instructions The post provides instructions for making a tool to un-pin the wire that you need to connect to the replacement part
I'm a little disappointed with myself for jumping to the conclusion that the wire insulation in my headlight had failed. As you probably know, removal of the headlight assembly requires loosening one side of the bumper. Due to my slow pace of work this required a few extra hours of my time. In my defense, I had to replace wires with deteriorated insulation in my Boxster and Mercedes headlights. My assumption was based on valid experience. Apparently the German auto manufacturers used a biodegradable wire insulation in the late 1990's through early 2000's. That insulation flakes off and causes shorts.
I remembered that when I purchased my Bi-Xenon headlights, the seller cut the wiring harnesses on one side of the car. The connectors were attached to one of the headlights when I received them. I found the connector that I would have un-pin when my repair parts arrive. I had an opportunity for an "out of car" practice session with them.
Although the poster on BenzWorld made his own tool, a commonly available tool can be used to remove the pin from the electrical connector. I've had this one for several years and I think I paid about $10 for it. It has come in handy several times. Tool for un-pinning electrical connectors. I used the prongs at the 12-o'clock position
Here's a picture showing the location for unlocking the connector: You can lightly pull up with a screw driver to unlock the connector. It will be obvious when it unlocks.
Here's a photo of the tool inserted in the connector: Make sure the connector is unlocked before pushing on the pin.
Here's a photo of the tool with two of the pins I removed:
It will be more awkward to do this job with the connector in the car. My repair part should arrive in two days and I will post an update stating whether this actually fixed the problem. I'm optimistic, but I've learned not to declare victory until I see evidence that the problem is gone.
I was able to install the replacement wire harness, but it did not solve the problem.
My previous check of the non-working side showed that there was some current to the connector with the emergency flashers on. I have an inexpensive Harbor Freight multi-meter and it was showing about 5 volts when I
tested it. I thought it was having trouble reading the voltage since it was transitory, but it may be that there is something in the system that is reducing the current in the circuit.
I'm planning to check the voltage on the working (passenger) side against the voltage I'm getting on the non-working (driver's) side. I will appreciate any suggestions from someone with expertise in automotive electrical systems.
A wiring diagram showing the locations and connectors will likely be important.
It could be a broken wire or bad connector. It could also be a bad SAM.
I suggest that you look at the pins at the SAM. See if you can "back probe" the wires.
From there, since this doesn't sound like a common problem, it's "divide and conquer". Try going ~1/2 way, and see if the voltage is there. Then, repeat for the questionable wire segment.
Automotive wiring problems "can" be **extremely** time intensive to find and fix.
However, ~99% of the time, it's a common (or happened previously) issue.
That's why Dealers have a Massive advantage in finding and fixing wiring issues. They check the system for similar previous problems, and what the solution was.
Of course, it a Dealer mechanic doesn't "get lucky", then even for a new car, the diagnostic time and effort may exceed the value of the car.
Yes, really! MB, BMW, GM, Ford, Honda, etc, have all taken back new cars, because the car/vehicle had electrical issues that took a month+ effort of an expert local mechanic.
Fwiw, Ford and GM wiring diagrams can be a big Joke! I have Four Mechanic Dealer wiring references for an '86 Ford Cars/Fox-bodies. NONE of them had the correct wiring information for my '86 T-Bird main wiring harness.
Hopefully, that type of BS (substituting wires with different color codes because of no availability for the correct wire) has stopped with cars becoming more electrically complex.
But, I still would not bet on it.
The connectors with the "pins" in them are (were/originallly) made by Molex, and the tool to get the pins out is a Molex tool. They're available online. As illustrated, they have tubes of several different diameters that can be used to depress the barbs on the pins, allowing withdrawal. Without the tool, anyone trying to nondestructively deconstruct a connector will need a goodly amount of patience, a sharp pick of some sort, and good eyesight.
Thanks for the suggestions and guidance. I'm currently taking time to research all the possibilities before attempting another repair. (In retrospect, I may have jumped on the first plausible solution and started "throwing parts" at the problem.) Here are the observations that I have made so far. I will appreciate a check of my logic regarding the conclusions based on these observations.
1. The turn signal on the passenger side works fine. This includes the LED's on the exterior mirror. If I remove the bulb from the passenger side, an error message stating that the bulb is out show up in the center display and the fog light starts flashing as a back up.
2. The driver's side turn signal bulb in the headlight assembly does not work. This is true even when I swap in the bulb that is working on the passenger side. The LED in the door mirror on the driver's side works fine. The fog light starts flashing and the error message stating that the bulb is not working on the driver's side displays in the message screen only if I remove the bulb from the turn-signal socket. If the bulb is in the turn signal socket of the headlight assembly of the driver's side, the fog light on the driver's side does not flash.
Based on observations 1 and 2, I've concluded:
a. That there is nothing wrong with the turn signal or hazard flasher switches.
b. Something is making the system "think" that the bulb is working. In other words, the circuit is drawing sufficient voltage to make it appear that it is working properly.
Observation 3 - I used my, admittedly inexpensive, multimeter to check the voltage that both the passenger and driver's side were reading when the emergency flasher was on. The readings on both sides were inconsistent, but the passenger (working side) more frequently read about 6 volts when the hazards flashed. The driver's side occasionally read as high as 5.85 volts, but not very frequently. This may be an artifact of my testing technique or my equipment. The issue is that you cannot just turn the flasher on and then probe the connection. I you do that, the system interprets the open circuit as a burnt-out bulb and switches power to the fog light. The probe I'm using to test the connector won't stay in unless I hold it. I'm planning to find a better way to make sure I'm making an accurate reading. At this time based on this, possibly unreliable, information I suspect that something in the wiring is damaged and some of the power is being lost before it can reach the turn signal bulb in the headlight.
Observation 4 - the wires from the headlight connector are difficult to trace directly back to the SAM. They leave the headlight and in about 6 inches they appear to merge with other wires and drop behind other components. They are wrapped in black cloth electrical tape and it is not possible to observe the condition of each wire. Based on this observation (and pending better measurement of the power reaching the connector) I think the repair may require me to access the wire at the SAM and connect a jumper that goes directly to the headlight. That way I can work around the possibly damaged section of the wire.
It is also possible that the SAM itself is damaged.
Again, I'm attempting to think this through before buying any more parts or starting to take anything apart.
Last edited by KevinH2000; 01-12-2020 at 06:31 PM.
seems to be working on the same issue I have. (The black/white wire he starts pointing to at around the 2 minute 30 second point of the video is for the turn signal in the driver's headlamp.)
Unfortunately, the video is not in English and I'm not able to determine exactly what he is planning to do to repair it.
I had a few minutes after work tonight and I did a little more testing.
I connected the replacement bulb socket to the power wire of the passenger (working) side flasher and the ground that I had been using on the driver's (non working) side fender. The bulb flashed correctly when I turned on the emergency flasher. This confirms that (1) the replacement bulb socket is functioning properly and (2) the ground I'm using is good. I'm now confident that the problem is either (a) the power wire or (b) the front SAM.
My next step will be to access the wiring in the SAM and run a jumper from the SAM to the power side of the replacement bulb socket. If that doesn't fix it, I will need to start researching replacement or repair of the front SAM.
I also found the next video in the series on SAM repair:
Picked up a used front SAM from another 2005 today
I picked up this from a non-running 2005 that I've been scavenging for about 6 months:
The only visible difference between the SAM I bought and the one in my car is that my car does not have a 5 amp fuse in the second socket from the top left. According to the chart I have, this is position #44 and was for the telephone. I'm hoping that won't make a difference.
I've been a "good customer" and the seller let me have for $20. I am not sure that I will need to use it or whether it is fully operational, but it is useful for the next step of my troubleshooting. Upon close examination, the wire for the flasher in the driver's side headlight assembly come from this connector: The white and black wire closest to the bottom is the one that powers the flasher in the headlight assembly.
There are several white and black wires coming out of the front SAM. Here are two more:
I had to look closely. There is a subtle difference between the wire in the first picture and the wires in the second. The first wire (the one I need) has two white stripes and two black stripes. The second photo is a black wire with a white stripe.
My next step will be to access the SAM in my car and install a jumper on the wire with two white and two black stripes. If that fixes the problem, I am stopping there. If that doesn't work, I'll connect the SAM and see if that fixes the problem. I'm reluctant to replace the SAM unless absolutely necessary, because (1) I have no way to test it to see whether it is functioning and (2) my car is a 6 speed and the SAM is from a car with an automatic transmission. The differences may be significant.
Last edited by KevinH2000; 01-19-2020 at 07:16 PM.
Too Busy to Work on the Car -Thinking About My Next Step
I need to find a day when I can devote a substantial amount of time to work on the car. I don't want to rush through the process of removing the SAM and initiating my next round of testing. In the limited amount of time I have this weekend, I did some work and considered some issues that I may need to address as I troubleshoot.
First, I don't think I can assume that the used SAM is trouble free. I opened the cover on the used SAM and visually inspected it. I don't see any visible signs of damage. No signs of corrosion or burned components on the part I can observe.
Of course, the circuit board can look good and have hidden damage. I have seen photos and videos of damaged SAMs and they they appeared discolored. There is no guarantee that the used SAM is good, but it is somewhat encouraging that the used SAM doesn't have visible problems and may be usable if mine is damaged.
Second - since my next step will be to install a jumper in the wiring between the SAM that is in the car and the headlight, I am wondering whether there is a method for opening this connector and unpinning the current wire and replacing it with the jumper:
For example, does the plate with the raised lettering at the bottom left of the photo slide off and allow the connector to open? I know I can cut the wire and splice in my jumper cable, but if the wire isn't shorted, I 'd prefer not to cut it.
My final issue regards the fact that my car has bi-xenon headlights and the donor car did not. When I added my bi-xenon headlights I had the car coded to accept them. Does anyone know whether the chip that holds the code for the headlights resides in the front SAM? If it does, I will need to plan to have the headlight coding updated if I replace the SAM.
Last edited by KevinH2000; 01-26-2020 at 01:03 PM.
I answered my own question about the SAM connector. The black plastic cap slides off with a little prompting from a screw driver.
The cap slides off and the internal part of the connector slides out.
I was able to unpin some of the wires with a jeweler's screwdriver. Unfortunately, I damaged the pin to the white/black wire. I will need to be extra cautious while working on the connector in the car. I was able to unpin a couple of the wires by pressing on the latch that holds the pin in the connector. I had to press on both the large opening on the right and the smaller opening in the middle while sliding out the pin.
I made a jumper that I can insert in both the headlight and the SAM connector for the next stage of testing. The larger pin with the blue rubber seal on it at the bottom of the photo will fit in the headlight. The smaller one at the top of the photo will go into the SAM connector.
I just need to set aside a few hours to access the SAM. It will probably have to wait until next weekend.
As always - suggestions, comments and critiques are welcome.
Because I am staying home on the weekends, I had some time to work on the car today. I first removed the SAM and tested the wire between the SAM and the turn signal for continuity. There was no indication of an open circuit and I proceeded to the next step of my repair plan and swapped in the replacement SAM. It was a tedious process.
The new SAM fixed the turn signal issue, but It created a different problem. My reverse lights now work when the car is in a forward gear or neutral, but not in reverse. I suspect that the problem is caused by some incompatibility between the replacement and original SAMs. The replacement came from an automatic transmission car and I have a manual transmission..
I will appreciate any suggestions for fixing the reverse light issue.
I reinstalled the original SAM and my mechanic copied the coding from it. I then removed the original SAM and installed the replacement (used) SAM and returned the car to the shop. The shop owner (who is an extremely knowledgeable mechanic who understands Mercedes) stated the he tried every combination he could come up with to code the replacement module. He would get right up to the very end but it kept saying that it will not code due to faults in the memory. He said the fault is for reverse light circuit short to ground. He tried with his Star machine and his Xentry subscription and had the same results.
My conclusion is that the replacement SAM (which I removed from a 2005 C230 with about 145,000 miles on the odometer) is also defective - it just has a different defect than my original SAM. I only paid $20 for the used SAM. It was worth a try, but I think it may be time to just buy a new SAM and ask my mechanic to code that. I'm not thrilled about paying approximately $200 for a new SAM. If anyone has other suggestions, please let me know.
Sucks but sometimes you gotta bite the bullet. I'm sure the guy spent more than $200 in labour trying to diagnose the thing. Win some, lose some. We've all been there. Good luck.
I ordered a new SAM. When I was researching the best price I ran across a review on the FCP Euro web site indicating that the one reviewer who provided feedback did not need to program the SAM. SAM Review
When I installed the used SAM it would have been “plug and play” if it had not been defective. That was a surprise because I have Bi-Xenon headlights and the donor car did not. Is it possible that the programming for the headlights is on the right front SAM?
I installed a new SAM today. With the exception of the back up light problem I had with the used replacement SAM, everything seems to be working OK without programming. I tested emergency flashers, parking, low beam, high beam and fog lights. The brake lights work and the interior lights work too.
This is a puzzle. The reverse lights functioned correctly in the original SAM both before I removed it and after I reinstalled it so that my mechanic could down load the programming from it. This leads me to minimize the possibility that I damaged a wire or connector when I installed the used replacement SAM and the new replacement SAM.
I will return the car to my mechanic and see whether he can program the new replacement SAM. I'm not feeling 100% confident that he will be able to do so.
I reinstalled the original SAM. The malfunctioning turn signal in the headlight assembly (which is mitigated by the turn signal on the external rear view mirror) is preferable to the problem with the back up lights I had with both replacement SAMs.
I have not quit. Another board member and I were successful bidders on a Mercedes Diagnostic Multiplexer & Ibm Thinkpad. I plan to learn how to use the system and apply that knowledge to solVe this problem.
As mentioned in another post, Jake and I are now the co-owners of a STAR diagnostic system. I used it to poke around in the Front SAM to see if I could solve the mystery of why two replacement SAMs fixed the turn signal issue, but created a problem with the reverse lights. As noted in my previous post, I reinstalled the original SAM and the readings I'm reporting are from that SAM.
Using STAR system, I accessed the following screens:
I'm planning to switch the setting from "Single Rod Gearshift" to "Old transmission (203) before model refinement." If that causes the reverse light problem, I will reinstall the used replacement SAM and see whether switching the transmission type solves the problem.
I thought it would be wise to ask for opinions before I possibly caused other problems.
01-05-2020, 10:48 AM
