JohnGalt1

Recently my 2005 C240 left turn signal started flashing rapidly when I turn it on, and the bulb stays lit solid while the car is on our off even without the keys.

I checked the bulb and even replaced it, and I swapped the whole bulb and socket assembly to the right side to isolate the problem but it only happens on the left. I also checked the wire harness at the connection point with the headlamp assembly.

The mirror signal and rear blink normally on the left despite the rapid clicking sound and rapid green arrow blinking in the instrument panel.

I also tried disconnecting the battery for 30 minutes with no luck.

Anyone's thoughts would be kindly appreciated.

Moviela

Is it only the front turn signal lamp that remains lit with the key out? When the car is started does the lamp go out or remain lit?

My initial thoughts are the rapid blinking is caused by a lamp out signal. Any turn indicator that is not drawing current causes this activity on the instrument cluster lamp and the audible indicator. Since you have a good lamp and socket, the usual cause of this indication of a burnt out bulb or disconnected mirror LED means we have a problem with the signal acquisition module or a wiring problem.

The rapid blinking can also be caused by too much current being drawn by a lamp. Sometimes people replace the lamp with one that draws too much current and the causes this indication. Replacing it with the proper part number solves the problem.

In this case I suspect a short to chassis of the wire between the lamp and the SAM. This could cause the lamp to be illuminated all the time, and cause rapid blinking.

I would start by using my eyes to observe the condition of the wiring harness for any abnormality, then wiggle the harness observing if the lamp goes out. Then would be a continuity test with the battery disconnected to determine if any conductors in the harness are connected together, or open from the lamp to their destination. Following that it might be easier to abandon the lamp wires in the harness and replace them with a new wire laced along side the harness.

JohnGalt1

Moviela,

The front left is the only lamp that stays lit, and both with the car running and while off with the keys out.

I verified the bulb is correct, and just to be sure I borrowed the OEM bulb from the front right and got the same result.

I tried wiggling the wiring harness where it plugs into the lamp assembly but there is no change.

Where is the SAM located, and what is a typical replacement cost? Can I trace the wiring from the lamp to the fuse to check for shorts?

Thanks for the feedback and taking time to help diagnose!

Moviela

There are two SAM's one in front under the fuses near the driver. The other is in the trunk on the fuse panel.

Your problem is not caused by a fuse. There is none for the signal lamps. They are driven by transistors in the SAM. The module is frightfully expensive.

You can follow the wires into the wiring harness, and they will arrive at the front SAM. Here is where a bright lamp and a critical eye can spot where the wires have been chaffed, nicked, cut, melted, harpooned, or dragged over a sharp edge.

JohnGalt1

A few weeks ago I removed the left fog lamp assembly because the lens glass was broken. I found an eBay replacement...from Latvia of all places.

In any event, the wiring harness was unplugged and sat in the bumper for two weeks before I put in the new glass and new bulb. I had wrapped the wiring harness in plastic to keep it dry. But this issue didn't start until shortly after removing the assembly a few weeks ago. They're close together and I'd imagine the wiring is near to the left flasher wiring as it runs to the driver side fuse compartment and left side SAM.

Any possibility this could narrow down the flasher problem?

JohnGalt1

Assuming that I have to replace the front left SAM, is this the correct part?


http://www.new-part.com/product/merc...FYEDOgodZQsAAw


I don't fathom having to do this, and I miss the old $5 flasher units. Why they'd consolidate into a device like this where one failure means replacement of a unit that does ten things is beyond me. My opinion of German engineering is hurting today.

Holmes5518

There's an updated turn signal repair harness for Mercedes 203 chassis. Call your local parts department, they'll know what you need. One per side is required. May or may not fix your issue, but it's cheaper than a SAM.

2 Repair set, USA version (white bulb socket), one side A203 826 02 82
2 Plug, rubber A000 545 78 80

Bailey9657

does anyone know how much is cost to replace SAM at MB dealer? my 2005 C240 in needs of front SAM replacement, or recommend a reputable independent shop who has MB DAS Xentry in Northern New Jersey,especially in Bergen County.
anyone with any info may also send me an email Bailey9657@yahoo.com

wvadam

the best way to tell is to undo the 3 t20 screws holding it in and read the part number off the side. There are several different part numbers for what looks like the exact same thing on the outside. I just replaced mine like this with a used one off ebay for $70 and it was a direct swap with no programming required. visually, that is the front sam unit you are looking for but the part number may be different for your car.

as far as the $5 flasher units, no cars are using those anymore. all the automakers are consolidating everything into modular computer based systems to actually improve reliability and make diagnostics easier (for the dealer) however when there is a problem now they can really make you pay for it.

Bailey9657

hi wvadam, i just got a quote for a left front SAM from a MB stealer for $1150 plus tax, and you're saying that if i could find a used one with the same part number there's no programing requirement. if that's the case i will wait and see if could find used part,any used part is better then $1200 thanks.

tommy320

Did you ever get this resolved? I have the exact same issue, 2005 c320

Thanks,
TT

tommy320

Bump. Any luck?

Russell Ormerod

If the front indicator lamp stays lit. You can be pretty sure you going to need a new SAM or have it repaired

Russell Ormerod

The reason why there is no more flasher units are because of extended vehicle networking. Everthing is on CAN bus. There is no direct connection to each lamp they all driven via a message on the bus. Front lamp are driven by front sam. Side mirrors by door module and rear lamps by rear sam. Even the indicator bulbs in cluster are signaled by CAN.

tommy320

Thank you. It's at Mercedes now, they are diagnosing. But I already have a feeling I know what they are going to come up with.

Russell, what did you mean by "repairing" .. versus replacing? Is there a procedure for repairing?


As a side note, things on my car sometimes stop working, only to work again in the future. Examples: small amber light in the bottom of the rear view mirror, the CD Changer, and the stereo. From time to time all three of these parts will stop working... then start again in a few days, or in one case many months later (CD Changer). Anyone ever had a front SAM just wake up one day?

Russell Ormerod

Well its possible to repair the front sam. I don't have a procedure for you because I usually wire them up on the bench and test the output stages. It's quiet a job just to desoldèr the pcb maybe around 50 to 60 joints to desoldèr to get to the component side. It's a pretty specialist job. You also need to be able to desoldèr surface mount parts. If you take it to MB they will not repair it. You will have to replace. As far as the rest of your issues. You would need to diagnose what controls those circuits. lamps in mirror I guess are controlled by OCP. The best way is to test with star. All easily fixed with the right testing equipment and technician. Good luck.

tommy320

Some additional feedback for those with this problem. The SAM shorted out due to water damage from the drains in the cowl being clogged. Per the tech the SAM was sitting in a small puddle of water shorting out the circuits. Keep in mind I keep my car very clean, but it was a used car and it had in its earlier years been outside where leaves/ debris could of entered. Also, I am not the first owner, so no idea of conditions before I owned.

If you have a SAM issue, a front SAM issue specifically, look into your cowl drains / all drains to ensure they are not clogged or blocked in any way. In this case I will replace the SAM. It won't be the cheapest way to fix this problem, a used SAM on eBay would be better, but it does get to the bottom of not just what the problem is, but WHY the problem occurred in the first place. I haven't found many forums that discuss the WHY, just the WHAT. Hope this helps.

Thanks for everyone's help.

Russell Ormerod

Yes a new SAM would be best in this case and will most likely fix your other intermittent issues as well