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I just discovered I had a fire in my trunk (2003 SL55)
I don't drive it often, so I have a battery tender connected to the systems battery (in the trunk)
Lots of damage. I believe its the battery control module that failed and started the fire - but not sure yet.
Anyone have experience with the extent of damages from this?
You're incredibly lucky the car and garage didn't burn to the ground. You've got a huge problem now. The body wiring harness is damaged and likely is no longer available from MB. Regardless, the labor to replace it would be astronomical. Who knows what other systems got shorted as well. The top hydraulic lines also run in that area. Call your insurance company. The car is totalled.
Last edited by E55Greasemonkey; 04-29-2023 at 08:55 PM.
This is one of the reasons I keep banging on about people who use battery tenders, if you cant leave your car for 4 or 5 weeks and it wont start, you have a battery issue or drain, Try using original Mercedes batteries they are very very good.
Unfortunately many of these cars have mystery parasitic electrical drains, finding them is time consuming and costly. There have been theory’s about what is causing this, but no real solution. This is a real problem for me and it’s not isolated or understood as to what is actually happening. Your factory battery hypothesis is great, but really has not been proven a solution.
I don't know that it's a mystery really. They have been documented here and on other forums.
Firstly you're flying blind unless you measure the quiescent current draw from the rear battery. Around 40 mA after the car has gone to sleep is what you will expect to measure. The car needs to be locked before you do the test, otherwise it won't go to sleep!
With a car of this cost it is only logical that an owner should be equipped with some good tools, like a DC milliamp meter to test the current drain. A known source is the siren module failing. Many just remove the 7.5 A fuse up front.
It does seem that genuine batteries last longer but a good AGM battery should last just as long as a genuine MB.
Looking at the photo of the fire damage, note that the BCM is intact and it's the wiring that's burnt. So I wonder what actually caused the fire?
As I have posted before, I use a quick disconnect on the rear battery and just take it out of circuit when I leave the car for more than a few days (I don't drive it much anyway). This permanently solves any battery drain issues and you never need to charge them up.
Plus a smoke detector in the boot in case it goes up while driving. You'd have to be unlucky but I did see a post here where it happened.
What’s a smoke detector going to accomplish when you either can’t get the trunk open or you’re not around.? A smoke detector allows you to get out of the house alive, but with an issue like this, the more logical thing to do is get rid of the car that could burn the house down. Get off the train track when the train is coming.
As for a smoking gun, there are theories about jump starting, aftermarket batteries, trickle chargers, and others, this car seems to have been sitting in the garage with a trickle charger on, which is really problematic.
You can hear it when it's in the boot, and you're in the cabin. My theory is that if there's a fire there while I'm driving, I'll hear it go off and have time to get out of the car.
Hope I never have to test that theory! For $10.00 it hardly matters.
I agree that chargers are an accident waiting to happen. They are well known for starting fires. It happened to a friend who lost a big shed and several cars.
And back to the original question asked, if you can’t repair this yourself, the car is effectively totaled. The wiring harness replacement requires almost complete disassembly of the car, extremely laborious, and as stated above, these wiring harnesses are very specific to the car and options and more than likely not available from the manufacturer.
You are looking at probably close to $1500 in junkyard parts: BCM, partial wiring harness, K57 and K75 relays, right frame lock cylinder, roll bar cylinder and right pawl cylinder, trunk trim, fuel flap line, strut plunger sensor and maybe strut, rear prefuse, keyless go antenna if you care about it. I have an '03 parts car that would have all of that intact except for the strut (not an AMG). It is not a small job, but doable. Car is technically totaled, but being an SL55, I would probably fix it if it were me.
The trickle charger (Duracell) was on a timer for two hours a day. After monitoring how long it took to re-juice the daily drain down, is how I arrived at the duration
So the car was just sitting, and hadn’t been run for a while when this happened? How old are the batteries? Sorry for the questions,and what happened, but I am seriously considering getting rid of the all 3 of these cars I have. This is becoming a normal event for these cars, and I have no interest in taking any part of this issue.
nobody knows what the issue actually is, but speculation from jump starting to bad batteries, to trickle chargers are hypothesized.
I like the car , and can deal with the normal but annoying crap and breakage, but am coming to the conclusion that if this problem can’t be resolved, I am not willing to own these cars.
When you say "partial wiring harness" are you saying I'd be able to splice in the harness downstream of any burned wiring?
Unfortunately that’s the only reasonable way to do it. Replacing the whole harness requires complete disassembly of the car. It can be done but it’s a great deal of work. I guess the question at hand is, do yiu want a car that has the potential to do this again? This isn’t an isolated incident and happens frequently, regardless of what is reported.
So the car was just sitting, and hadn’t been run for a while when this happened? How old are the batteries? Sorry for the questions,and what happened, but I am seriously considering getting rid of the all 3 of these cars I have. This is becoming a normal event for these cars, and I have no interest in taking any part of this issue.
nobody knows what the issue actually is, but speculation from jump starting to bad batteries, to trickle chargers are hypothesized.
I like the car , and can deal with the normal but annoying crap and breakage, but am coming to the conclusion that if this problem can’t be resolved, I am not willing to own these cars.
sigh.....me to. I was thinking about swapping over to coil overs but crap like this continues to turn me off. Thinking about moving on
So the car was just sitting, and hadn’t been run for a while when this happened? How old are the batteries? Sorry for the questions,and what happened, but I am seriously considering getting rid of the all 3 of these cars I have. This is becoming a normal event for these cars, and I have no interest in taking any part of this issue.
nobody knows what the issue actually is, but speculation from jump starting to bad batteries, to trickle chargers are hypothesized.
I like the car , and can deal with the normal but annoying crap and breakage, but am coming to the conclusion that if this problem can’t be resolved, I am not willing to own these cars.
That is correct. Been sitting for about a month. Discovered the issue when about to start / run the vehicle
They were puchased, along with the Duracell Ultra (1.5A) automatic charger in 2019 - so just about 4 years. This was purchased after the second battery I had purchased failed after a short period of time.
Everything worked well for 4 years . . .
I like the car , and can deal with the normal but annoying crap and breakage, but am coming to the conclusion that if this problem can’t be resolved, I am not willing to own these cars.
It's certainly a concerning issue. There's a good FB group out there dedicated to this issue and sharing information on it.
Digging into the matter a bit, this is what I have on the board:
Most of the instances trace to the early R230s (2003 - 2006). I've encountered examples with the first facelift (2007 - 2008) and even one with the second facelift (2009+) but those thankfully have been few and far between.
MB superseded the part number for the BCM and the latest is backwards-compatible with all R230s.
In many cases, there are warning signs if you look (damaged board, capacitors, etc.).
What I've done thus far as preventive measures:
Nothing that touches the electrical system is modified from stock. No aftermarket multimedia units, not even tapping the fuse box to hardwire a radar & dashcam.
Accessories are plugged into a 12V splitter with a kill switch that I toggle on / off regularly.
For Winter storage, both batteries come out of the car. They are charged, tested and maintained.
What I am planning to do further:
Install a compact, self-activating fire extinguisher above the BCM.
Replace the unit proactively with a Genuine Mercedes one and replace both batteries with Genuine Mercedes as well.
Treat this as preventive maintenance every 5 years or so.
04-29-2023, 07:24 PM
