Sulfur burning smell coming from trunk/battery.
 

Has this happen to anyone? Battery is fairly new, car has been sitting for 5 days because i was on vacation, came back and the smell from the cabin was awful, traced it to the battery area, coming from the battery. Did something get shorted? There was some water inside the trunk but not much. Car still started and drove fine, just got the red battery sign and visit workshop on the dash.

It's likely the electronic module in the trunk area
 

There have been many SL230 Trunk Fires! This is a serious fire hazard that MB is yet to address!

This fire hazard is an issue for ALL 230 SL Class Vehicles from 2003-2012 and may also be an issue with the new 2013 through current year 231 Series of SL Class vehicles.

It's likely not the battery like you think...Click on the thread below and be sure go to YouTube to view the video referenced there so you can see the exact location of the culprit (an electronics module) that tends to short out and is causing all these SL trunk fires. Again, this is a very serious fire hazard...Get your 230 SL to a MB Dealer so it can be checked out ASAP!

https://mbworld.org/forums/sl-class-...runk-fire.html

Man the smell has been going on for a couple days, i thought it was just a bad battery. I'll have to go home later and open up the part and see if it's fried like that.

Below is a link to a video showing one of these SL Trunk Fires in Hawaii. This particular incident occurred with a new 2012 SL550 and again, the car had not been driven and was parked in the garage. Luckily, this guy found it before it erupted into flames and burned down his house. In the last minute of the video you can see the electronics module, (the culprit responsible for these fires), because the right side trunk lining is burned and removed. Still smoldering however. My own 2003 incident was actually much worse than what occurred in this video but you can plainly see it happening nevertheless. This ruins all the car's electronics, the car will not start and the trunk will be locked. You will have to use the flat key from the key fob to open it. Once you get the toxic black smoke inside your SL, you will never get the smell out. If there are flames present, and the Fire Department sess there is smoke iside the car, they are likely to spray water and/or chemicals inside the passenger area as well as the trunk. Due to this damage, your SL will most likely be considered 'totaled' by your insurance company, but don't expect the check you receive to be nearly enough to replace it.

Click below to view the video and note the location of the electronic module in the very last minute of this video.

I have a total of 19K or so into my Car, i doubt Geico will give me anywhere near that if it's indeed totaled. But strong hazard smell coming into the cabin, it was nauseating to drive, i parked it and took another car to work thinking it was a battery. I need to open up everything and look at it.

The car has sat for 5 days prior to smelling this, i checked the vent tube and it's pointed to the floor outside of the vehicle. Other than the strong toxic smell, car still drove and behaves fine, i can lower and raise the roof and all functions work, except i get the red battery sign on now when i start.

Well, if the module is the source of the smell with your SL, I can tell you this: The first hint of this problem is a very strong electrical (burning) smell as the electronic module overheats. Eventually it becomes hot enough to smolder and destroy the module, which only increases the electrical current, (heat). Soon the smolder burns its way through the trunk lining allowing more oxygen into the trunk, it can then erupt into flames which easily melts away the aluminum body just beneath the fuel filler cap. That's precisely how my incident happened. (Yes, there is real danger of an explosion anytime your gasoline filler tube is in such close proximity to fire and flames).

Most every trunk fire report I have seen shows that the module is overheatied and ignited while the car was PARKED, (often in a home garage). Mine had not been driven for 3 days when the fire occurred. If you don't notice the burning smell first, you may not notice the smoke either becauset the toxic black smoke initially just fills the inside of your CAR, assuming you left the top and windows up. (It's really quite amazing just how air tight these cars are). Only after the module has burned completely through the trunk's lining are you likely to see a lot of smoke inside the garage itself. (You may have noted that from the video).

Do not leave your SL parked in your home garage! It is one thing to lose the car to this hazard, quite another to lose your home and risk your life and the lives of your family. You may have smoke detectors in your home already, but consider one for your garage if you haven't already. I also recommend a carbon monoxide detector for the garage as well.

The part that catches fire is the Battery Control Module. I'm not sure what happens, but some suspect that the trunk lid seal around the rear glass deteriorates and lets water in, which damages it. If you smell this "burning", I'd get it fixed quickly. I'd probably even disconnect both batteries to make sure it can't start an electrical fire.

Yeah, the Dealer mentioned that to me too, but I do not think that was the cause for me. Mine certainly hadn't been driven recently in the rain, and in fact, had been parked inside a very dry garage for 3-days, and not driven at all over that time period. There was not any water present when it occurred, and I can't remember a time when I noticed any water seeping from the rear glass into the trunk area before. If indeed moisture played any role in my particular incident, it was more likely the humidity in the that affected it somehow.

Unfortunately, I believe these fires are actually an example of 'spontaneous combustion' where this module can simply 'short out' all by itself without ANY obvious cause to trigger the event! I don't think it's prior water damage or even the 'aging' of this module and/or all of it's wired connections. In fact, if you look at the posted video which was from 2013, it was a virtually 'new' late model 2012 SL550, one of the last 230 series made..

(Note: The 2013-to-current SL 231 Series vehicles also have this module).

I did not realize that the R231s had a dual-battery system. I thought they only used that with SBC-equipped cars. And SBC was discontinued as of MY2007 for all but the R230 SL (since it's chassis could not easily be retrofitted to handle a vacuum operated brake booster).

My understanding from the Dealer is that the fire culpirt is actually a Multi-Function Electronics Module, and therefore controls multiple electronic devices on SL series vehicles.

The box shown in the last few seconds of the above video is the dual-battery control module. Maybe other models with single batteries mounted in the trunk have some sort of control module there that could still fail?

Will have to bring the car in to MB and have them look at it, i opened up the rear trunk area and didn't see anything on fire, just smelled so bad, as soon as you open my trunk your eyes will water. It's toxic, i don't even feel safe driving with the top opened.

MB didn't have any availability for service, I took matters into my own hands and traced the smell to the BCM. As suspected, the module must've shorted inside and is emitting a very strong odor through its casing. No other wires outside look like it shorted, and my sniff test confirmed the strongest smell is coming from the BCM.

https://c1.staticflickr.com/1/857/42...b39f2387_h.jpg

The hard part was getting to it, to replace it looks like cakewalk. I will order one used on ebay and see if it'll stop the burning smell and make the Battery light visit workshop light go away.

Electronics Module Shorting Out
 

Glad you found the source before something catastrophic happened! You dodged a bullet here! Best to disconnect the batteries for now until this module is replaced! These modules can short out for no apparent reason.

I removed the trunk battery thinking that was the one feeding the BCM, however the smelled still persisted in the morning, so the starting battery in the front also supply power to the BCM? it was still hot this morning, so i removed that.

Yes, it's best to disconnect both batteries until the problem is resolved!

Yes, in fact, when the consumer (rear) battery is disconnected, the BCM will switch the starting battery into the circuit. to power the basic consumers. You do need both disconnected. And always disconnect the consumer battery first and reconnect it last.

I ordered a new BCM and it's on the way, any bad thing that'll happen to the car for having both batteries disconnected for a week?

No, but you may lose a few settings that you'll need to redo. The side windows will need to be normalized - lower them, then raise them with the button held in the second detent for about 10 extra seconds. If you get an "ESP Not Available" message, you'll need to reset the steering angle sensor - start the engine, and in park, turn the steering wheel fully lock to lock a few times until it clears. You may also lose the sound settings on the radio (though not station presets).

Rodney, interestingly enough, when i disconnected both batteries for a couple days, nothing was lost. I didn't have to do anything afterwards, my memories are still there and didn't have to do any ESP calibration. Got lucky i guess.


Anyways, here's the damage to the BCM. A couple of the capacitors burned and damaged the PCB board. Here's something interesting that happened after i put a new one in, my car used to get heat soaked like crazy, it's only stupid fast within the first 20 minutes of driving, after that, it's only fast. Now it's stupid fast all time, i'm not sure if this new BCM is turning on the intercooler pump or it's strictly placebo, but something definitely happened. Also, the car had some shaking, like mini misfires at idle, that's gone too.

https://c1.staticflickr.com/1/861/42...a7e317f7_k.jpg

https://c2.staticflickr.com/2/1792/4...98c80fcf_b.jpg

https://c1.staticflickr.com/1/932/43...e65eb040_b.jpg

Let this be a warning, if you've got a burning smell in your trunk, open up the lining and sniff the BCM, you don't want a fire, i think mine is on the verge of engulfing in flames. It's real easy to open the cover panel, just 4 T15 torx to see inside the board, and it's 4x 10mm to completely remove the BCM from the bracket.

Wow! it looks like you got that fixed just in time.