Mods: There is a duplicate thread in the W204 area. Let me know which location is more appropriate.

Hello everyone, I'm brand new to these boards. I bought a 2012 C350 Sport with 30,000 miles last week.

I've been super happy with the vehicle except something came up on my way to work this morning. I couldn't find anything anywhere on the internet regarding this issue, so I figured I would see if y'all knew what the issue could be. The rear speakers (I think it's the rear deck sub woofer/tweeter), started to crackle... about 10 minutes later an extremely high pitched screeching started to emanate from the rear of the car (It's unbearably loud). Attached is a video I recorded on my phone. It sounds like a grounding issue to me. Has anyone experienced anything like this? I'm not averse to popping a few panels to get at the wiring, just wondering if anyone had anything like this and looking to tap into some experience that someone else might have.

Many Thanks,

 

Update:

The same day the rear deck speaker buzzing/screeching happened is the same day it stopped. However, whenever I open the car door, or start the engine, it briefly "chirps", as my wife puts it, with a very brief version of the high pitched buzz/screech. I got some body panel tools in this morning, so I'm going to remove the rear deck this weekend and see what it is. I have a feeling something isn't properly grounded, or the speaker is dead. I checked the rear amp in the trunk and everything is hooked up properly. I doubt the amp went bad, but it may have. I'll keep the thread updated in case anyone else has the same issue. I plan on removing the rear deck to get access to the speaker this weekend. If it's faulty wiring/connection, it should be an easy fix, if the speaker is dead, I'll have to find a replacement online, either new old-stock or used, probably used since it seems new old-stock goes for over $400 for the rear setup alone.

I'll also post photos.

If anyone wants to chime in and tell me what they're thinking, I'd really appreciate it.

 

Update 2:

So I was able to remove the faulty speaker. I had to remove rear bottom seat cushion to remove the side bolsters to remove side bolster fastener plate underneath to remove the C pillar covers to then fold down the rear seats and remove the rear deck. (Pretty easy actually, it's all clipped in, the only tool you need is a socket to remove the two bolts holding down the bottom of the rear seat side bolsters). Once I removed the rear deck, I unplugged the faulty speaker and then twisted it out of its mounting slots. It was definitely a faulty speaker. The cone does not oscillate softly or easily. If you apply enough force (gently), it comes "unstuck" and moves to the bottom of its travel only, then will snap back to its original position and get "stuck" again. Either way, blown speaker.

So just this week, the whole speaker system started to crackle loudly and the cabin filled with the smell of burned plastic. It sounds identical to fosterelli's issue here: https://mbworld.org/forums/e-class-w...melting-3.html and MBTAF's issue here: https://mbworld.org/forums/e-class-w...ed-smoked.html I get the feeling that the two speaker issues may be unrelated. But then again they could indeed be related.

Since I live in the Dallas area, I will be taking it to MB Plano to check it out. I will try to follow konigstiger's advice here: https://mbworld.org/forums/e-class-w...ml#post7229005

Just as a reminder, the vehicle is a 2012 W204 C350 Sport with the HK sound system bought with 36,000 miles and now has 40,000 miles. It is effectively out of warranty, but it seems like MBUSA is willing to work with people regarding this specific issue.

I have a video file that I took of the speakers crackling and burning. It's too large to attach, so I'll have to find another way to get it sorted.

I will try to keep this thread updated for posterity. If anyone has or had a similar issue, let me know what your experience was with getting it sorted, I would really appreciate it!

 

Update: 3

I think I found the culprit for the speaker crackling. And it's totally different from what I thought. The amp for the sound system is in the trunk of the car on the drivers side behind the "first aid" panel... That whole area was wet. It had rained hard the night before. I grabbed a bottle of water and ran it down the roof line in order to try and identify where the leak was. There are rubber coated pegs that fasten part of the exterior trunk liner seal. The top most corner had a really rough looking peg that looked like it was removed at one point and replaced in a ham-fisted manner. The water dripped right past it and into the trunk... right on top of the amp where it plugs into the wiring. I unfastened the driver side of the trunks interior liner, pulled it down, and unplugged the amp and unbolted the amp mount. I took the whole thing inside and disassembled it and cleaned it with isopropyl alcohol and made sure everything was dry. I also cleaned all of the connections and cleaned the cable connections with isopropyl alcohol and a tooth brush. I dried out the drunk (thankfully no rust). I've temporarily plugged the leaking part of the trunk until I can stop by the dealership to get some new rubber stoppers for that liner. After buttoning up everything, the sound system worked perfectly.

If anyone has experienced speaker crackling with the smell of burned plastic, the system is shorting out. Mine happened to be a failed trunk seal that was allowing water to drip right on to the amp. If anyone has any questions, I'll monitor this thread occasionally. Feel free to private message me also. Thanks.

 

I've heard of this sort of thing happening before - glad you figured it out!

 

Thanks Mr. Toad

I have a feeling that the small 3" speaker in the rear that I initially removed (have yet to replace, trying to find a decent example on ebay that isn't beat to hell), was blown out by the amp short due to water coming in. It is by far the closest speaker to the amp with the least resistance between it and the amp out of all of the speakers and may have taken the brunt of the effects of the short. However, when the system was crackling in general, it seemed all of them were doing so, so who knows. I may end up getting a complete set (gently used if possible) anyway just to make sure everything is fresh. I wouldn't be surprised if the speakers were damaged by the short because of the odor I smelled (burned plastic). I've got door panel tools and a rivet squeezer for pop rivets so doing the door speakers should be easy!

 

Same thing happened to me today with the amp getting wet during the rain . Did you have any luck finding those little rubber stopper/clips? After a couple hours of drying mine seemed to stop popping/smoking but I can’t tell if anything is broken. We’re any of the speakers broken on yours ?

 

I have a 2014 C300 and this problem just happened few days ago when raining hard. Did you end up getting the new rubber stoppers? Can you tell me which one to get? Thanks.

 

Hey dude. Did you ever find a fix or what was wrong? I have the same sound issue as op but no water inside the car. Trying to figure it out.

 

Nope. No one replied.

 

so you left the problem as is?