CLC180 W203 - Potential malfunction of the overhead control panel (OCP)

[Captiva]

Greetings everyone
Recently acquired a CLC180 coupe. [EDIT: It appears that this model is actually a CL203, not a W203 - my apologies] I have a matter on which I would appreciate your pooled expertise. I have conducted a search. I apologise for the length of the post; I prefer to offer comprehensive detail.


I purchased this automobile a few weeks ago. Week one, no complications.

On Friday, at the conclusion of the first week, I will have an auto-locksmith fabricate and program a new key, as the car was supplied with only one key. He encountered difficulties reprogramming the keys to my original ignition module (EIS), so to facilitate my mobility, he installed a temporary spare EIS until he procured a new. This could be pertinent to the narrative.

On Saturday, I completed many long runs; nevertheless, on Monday, I awoke to a depleted battery. I observed that the ambient light beneath the rearview mirror is perpetually illuminated, regardless of the circumstances. It does not deactivate upon removing the key from the ignition, nor does it cease operation after a delay. The onboard computer lacks possibilities to modify the behaviour of this light. All other internal lights function properly and deactivate as anticipated when the doors are closed or the vehicle is locked. My wife possesses an SLK, and its ambient light deactivates immediately upon turning off the ignition.

The locksmith returns with the new EIS, and I recount this narrative to him. I request that he reinsert the original component to determine if the ambient light deactivates. It does not. He installs the new replacement EIS. The ambient light remains lit. He proceeds on his path.

I am currently in parasitic draw mode. At steady state, once all doors are closed and a period of time has elapsed, the current draw is approximately 0.17 amps. I begin removing fuses, and ultimately, the system ceases operation when I extract fuse 9 from the fuse box in the trunk. This fuse is likely intended for the overhead control panel (OCP) control box. Upon removal, the ambient light extinguishes, and the current draw decreases to approximately 0.08 amps. I have heard that 0.05-0.08 amps is permissible, hence it is at the upper limit.

Meanwhile, I consulted a Mercedes-Benz dealer regarding this matter, and they recommended disconnecting the ambient light from the OCP. I successfully disconnected two connectors, one for the ambient light and another of uncertain use, so significantly decreasing the power usage.

I have disconnected these two. The white object on the right corresponds to the ambient light in the mirror.

[Captiva]

This morning, the vehicle was entirely unresponsive to the remote unlock; yet, I successfully unlocked and started it, so alleviating the issue without addressing the underlying cause.

Therefore, my enquiries are as follows:


- Is it plausible that the pull responsible for the flat battery was not present during the first week, considering I experienced no power concerns until that time?
- Could the unidentified transient EIS have triggered a malfunction in the electrical system?
- Do we believe that the OCP is defective?
- I have encountered information regarding a SAM that may also be involved. Is it possible that a SAM is defective?
- Could someone inform me which SAM it may be, as I suspect there are several possibilities.
- Can someone provide guidance on how to test the SAM, considering I lack access to any STAR or Autel devices? - Additionally, please include any other relevant information I may have overlooked.

Thank you in advance.

[BizarreBleak]

Did you purchase the vehicle from a dealer or through a private transaction?

[BizarreBleak]

Does this resemble what it appears to be?

[BizarreBleak]

[Syncephe]

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[Liveek]

They require coding for the vehicle utilising STAR, I believe.

[Captiva]

sold as seen; therefore, I believe there is no recourse. Furthermore, I cannot ascertain with certainty if the defect existed before the important individual performed his actions.

[Captiva]

Affirmative. One of those items.
Switch placements are irrelevant since the ambient light is non-switchable, and the switchable ones function correctly.

[Captiva]

I have previously completed this process and established that the draw occurs through the OCP circuit. I demonstrated that disconnecting the fuse in position 9 of the boot fusebox eliminates the continuously illuminated ambient light and normalises the power usage.
My enquiries now pertain to whether the error is probable in the OCP or in another component, such as one of the SAMs. And how I may diagnose.
Thank you.

[BizarreBleak]

The phrase 'sold as seen' is unlawful unless one is a merchant or operates a business. The trader cannot compel you to relinquish your consumer rights if you are a private consumer.

If you are aware of your purchase and wish to be equitable with the trader, then rectify it independently. Legally, the trader is obligated to rectify the issue, unless the purchase was made for trade or business purposes.

[Captiva]

Does anyone possess knowledge on how to effectively detach these connectors without causing additional damage?

I cannot see a lever or a clip, yet they are quite difficult to remove.

[Adv3nture]

A few matters. This is merely my perspective.
The LED in the mirror would likely consume approximately 20mA. The measurement of 170mA suggests that an additional load is also using current.
Despite a 170mA draw, I anticipate it would require several days to deplete a completely charged battery in optimal condition.

I cannot identify any rationale for the circumstance you outlined regarding the key to be the source of the issue you are experiencing.
Affirmative. In my modest opinion, I would suspect the OCP controller; nevertheless, substituting it with a verified functional unit is the only method to ascertain certainty.
That constitutes the extent of my understanding, but I hope it is resolved promptly and economically.

[Captiva]

Thank you.
I have a pre-owned replacement OCP en route.
I will be able to definitively ascertain whether the ambient LED resumes normal functionality, as it currently exhibits a persistent problem (i.e., it remains continuously illuminated).