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2011 SLK350
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Discussion Starter · #1 ·
Hi,

I’ve been a member here for a few years but this is my first post.

I’ve got a 2011 R172 SLK350 that, as the title states, it wakes up on its own. When I park it and return to it, I sometimes find it in one of three states. Either with the radio/accessories on and the wipers in the vertical position, with the wipers in the vertical position and a totally dead battery or with the wipers in the vertical position and the battery still able to start the vehicle. It has keyless entry and keyless start and this occurs regardless of whether I leave it locked or unlocked. If its left in the locked state, the car cannot be opened by either grabbing the handle (keyless entry) or by the button on the remote. The only way to unlock the vehicle is with the key hidden in the remote.

It’s been happening for a few years now, initially very rarely, maybe 2-3 times a year but now a few times a week. Today it‘s happened 3 times! I’ve had my Mercedes specialist mechanic look at it but they haven’t found anything. Scanning the vehicle provides no details.

I suspect it has something to do with the keyless start but its only logic that leads me to this diagnosis, nothing concrete.

I was wondering if any members have experienced this or if anyone has any troubleshooting ideas. I’m both mechanically and electronically literate, being an Electronic Engineer and working on my own vehicles.

Thanks in advance,
Pat.
 

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2009 SLK350
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478 Posts
It sounds like you are much more knowledgeable than I about such things but I'd start with the windscreen wipers and isolate them to see if they are causing the problem. Sounds like a headache problem.
 

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One thought, completely random.

We find it very easy to either forget to put in Park, or forget to stop the engine. This is a C class 2015.
I hate stop/start. More trouble than it's worth.

I wonder if P is not properly engaging. I do not know, but that might leave the systems active.

I'd also leave the wipers in the off position every time the car was switched off.
 

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2011 SLK350
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Discussion Starter · #5 ·
Thanks for the comments.

When I leave the car it's all off and wipers are in the parked position. It's only when I return that systems are on and the wipers are vertical. It doesn't have start/stop, just keyless push button start.

I've actually seen it "Wake up" once or twice and the wipers move from parked to vertical, dash lights up and the radio turns on. Car doesn't unlock on its own though.
 

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115,268 Posts
Do a battery reset yet to clean out the gremlins?
 

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2011 SLK350
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11 Posts
Discussion Starter · #9 ·
JBanks, It would have done a reset the last time it drained the battery, which was about a month ago, but I will disconnect the battery overnight tonight and give it another go.

Funnily enough, my wife was only saying yesterday that the car is possessed :eek: Anyone got a number for those guys?
 

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2012 SLK350
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Battery drain so the car won't start is not a reset as there's still power going to the car. You need to disconnect the battery and let it sit for at least 30 min.
JBanks, It would have done a reset the last time it drained the battery, which was about a month ago, but I will disconnect the battery overnight tonight and give it another go.

Funnily enough, my wife was only saying yesterday that the car is possessed :eek: Anyone got a number for those guys?
 

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2011 SLK350
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Discussion Starter · #12 · (Edited)
Hi nplenzick, I know what you’re saying but it was in this case. Battery was totally dead, less then 2v. It was so flat that my charger wouldn’t even start charging. I had to manually charge it with a power supply first to get it above 6v so that the charger could recognise the battery. I also disconnected the battery to charge it so yes, the car had no battery connected for about 8 hours or so.
 

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2006 SLK350
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686 Posts
You're in AUS so I'm guessing rainwater ingress can be eliminated?
 
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2011 SLK350
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Discussion Starter · #14 ·
It does rain down here :) but the car seldom sees wafter. It is garaged in a warm, dry (not humid) garage. It probably spends no more than 10-15 hours per week outside of the garage. All seals seem to be in tact and there’s no water where it shouldn’t be.

Looks like I’ve stumped everyone here. I was hoping someone would say Yes I’ve seen that before….Replace xyz. I knew this issue was going to be almost impossible to fix without just blindly replacing expensive modules. But then it might be something as simple as a faulty ground connection, door lock micro switch, or similar.
 

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2013 SLK250 CDI
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143 Posts
I don't have an answer but have you removed the keyless button from the ignition switch, hidden it in an RF blocking pouch away from the car and reverted to a key operated switch? I have no idea why the wipers should go to a vertical position and there may be something in the wiper motor that makes this an 'off' position but for the wipers and the radio to start operating, the ignition circuits have to be made live and something in the ignition switch must be calling for power. I know that if I leave a key in the ignition of one of my other cars, the car will appear to go to sleep after a while but will continue to drain the battery in a very short time - 3 or 4 hours. I wonder if it could be that the keyless button has an internal fault that is perhaps temperature affected and that strange signals are flying around the wiring at random times.
One other thing - is the main battery relatively new?
 

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2006 SLK350
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It does rain down here :) but the car seldom sees wafter. It is garaged in a warm, dry (not humid) garage. It probably spends no more than 10-15 hours per week outside of the garage. All seals seem to be in tact and there’s no water where it shouldn’t be.

Looks like I’ve stumped everyone here. I was hoping someone would say Yes I’ve seen that before….Replace xyz. I knew this issue was going to be almost impossible to fix without just blindly replacing expensive modules. But then it might be something as simple as a faulty ground connection, door lock micro switch, or similar.
I get that. I often check here for the same to save me time. It's always nice when someone says, 'they all do it' - it's this :)
I am not familiar with your car (I have a 171) but the symptom that sticks in my mind is the wipers. On my car if they are physically turned off, that's it. Unless they are on rainsense setting they will not come on....because they are shut off.
I would tend to weigh that heavily in the diagnostic process. If it's getting worse that's not always a bad thing but I don't think you're going to find it's 'simple' like a bad ground or switch.

Something is powering the wiper circuit..even when it is physically turned off.....that's where I would start. If you can answer how that happens, you might have 'the' answer.
 
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2011 SLK350
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Discussion Starter · #17 · (Edited)
@TimGriff6 good suggestion about removing the push button. I’ll try that.

@marvin-miller The wipers are constantly in the auto (rainsense) position. I’ll move them to OFF to see if the wipers moving stops. And yea, microswitch or bad ground is just wishful thinking.

Battery is not new and has been drained fully a few times because of this problem but it starts the car easily, even after a few days. I’m reluctant to change the battery without resolving this issue as I don’t want to kill an expensive AGM battery by draining it completely.
 

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Forget about the battery, as you said, at this point it's sacrificial. I was under the (erroneous) impression that the wipers were off. With cases like this, it's often a question of where to start. If it continues to do this with the wipers in the Off position, you have a starting place, and that alone can be a tremendous help.

On the other hand, if it stops doing it with the wipers off, then that too sheds more light on it :)
 

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2013 SLK250 CDI
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143 Posts
You will find that the battery will still start the car even when it is on the way out but other strange things happening indicate that it needs replacing. On mine stop/start and Comand were playing up. There are loads of other symptoms of a failing battery in the forum if you search. Think of the cost of a battery in terms of dealer fault finding hours because if it needs replacing, trying that until the fault recurs probably won’t kill a new battery. If it doesn’t cure it, swap back until the fault has been identified and then put the new one in.
 

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2012 SLK250CDI
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You will find that the battery will still start the car even when it is on the way out but other strange things happening indicate that it needs replacing. On mine stop/start and Comand were playing up. There are loads of other symptoms of a failing battery in the forum if you search. Think of the cost of a battery in terms of dealer fault finding hours because if it needs replacing, trying that until the fault recurs probably won’t kill a new battery. If it doesn’t cure it, swap back until the fault has been identified and then put the new one in.
I have to agree with the above, low voltage in our cars can produce some really weird faults, I would suggest a quick check on the battery voltage as well, got a feeling it could be a bit below where it needs to be!
 
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