My new B200 keeps unlocking itself overnight.

[Rob7seven]

When I got my new B200 a few months ago, it was the first car I'd had with keyless entry, which took me a while to get used to and trust. I thought I had it all worked out, usually locking the car by touching a door handle and listening for a bleep and watching the mirrors fold in, but I'm beginning to wonder if my trust is misplaced. The car is almost always parked at night at the side of the house under a substantial weatherproof carport, and it seems to have developed a habit of unlocking itself while we sleep. I think it's happened about three times now, once about a month ago, then one day last week, and again last night. Wife Anne usually takes our dog out last thing at night, and she'd have noticed if the rear hatch was open, which it never has been, and this morning she saw that the rear hatch was open. Each time, the keys were sitting on a chair in our bedroom, and there's no way they could have been touched, so how could the car have unlocked itself? Anne thinks she'd have noticed if the mirrors had unfolded themselves, so it appears to be just the rear hatch that's affected, and all four doors would have remained secure, the spare keys live in a desk drawer. Does the hatch only unlock with a kick if the keys are held by the kicker? Anne suggested a cat or malevolent fox wandering underneath the car, but surely that's not possible?

Local Dealer Sandown are looking into this to check if it's happened before, but they had no immediate answers, so has this occured to anyone else on here, and any suggestions?

 

[DREAMER NO2]

W

 

[DREAMER NO2]

Well all i can think of is ...When i go to charge my battery- with the doors locked ,once i remove the negative lead the doors unlock .So its a must be when the circuit is broken . [ Not the same car you have ] just an nidea

 

[SL63 Mark]

Sounds like the kicker is at fault, maybe a cat, or blown debris is setting it off, while your keys are in range. Try keeping them in a Faraday pot. (Solid metal container.)

 

[Rob7seven]

The more I think about the problem, the more confused I get, I don't think there are any simple answers. I know that there can be problems when electric circuits are broken, but the battery has never been moved or disconnected as far as I know, the car is only just over three months old. It did spend a few hours at MB Dealer Sandown last week, they wanted to replace the centre console to cure a rattle that I'd been unable to cure. All they achieved was to make the rattle worse, I can now hear it all the time, and it's now in the main facia as well. They're having the car back next Tuesday, so they can have a second attempt at fixing that, as well as trying to find out why the hatchback is springing open of its own accord. With the stray cat or blown debris theory, how could that happen? Surely all current MB keys go to sleep after a few minutes if they don't detect any movement. I'll have to check on this, but I understood that in any case, the key has to be within a metre or so to the car to have any auto-unlocking effect, so a cat would have to have my keys somewhere about its person to enable the car to register it, either that or one of those signal attenuator things that I'm told car thieves can find on eBay.

All I've been able to come up with is maybe the door's latch or locking mechanism is faulty, and doesn't always clck into place fully. So far this phantom opening has happened about one month ago, two weeks ago, and again just last week. Thinking back, I think it might have done this on one or two earlier occasions, but I dismissed this as me not locking the car properly, but I hope we'll all be wiser after Sandown have gone over the car again next week, watch this space.

 

[DREAMER NO2]

OK good luck at Sandown .

 

[KennyN]

Get a signal blocker pouch and keep both sets of keys in it every time you get home , this will eliminate any potential issues with the keys.

If there are no issues over time then the problem is with the vehicle itself , either that or the TV remote is on the same frequency as the car so every time you access the "Adult Channel", the boot raises.

K

 

[Rob7seven]

Get a signal blocker pouch and keep both sets of keys in it every time you get home , this will eliminate any potential issues with the keys.

Nothing wrong with that advice maybe, but my car's problem isn't anything to do with keys, it's something to do with the hatchback's locking/closing mechanism.

Two days ago in a Waitrose car park, I opened the hatch, not sure but I probably did the usual kick under the bumper. Put shopping in the boot, and pressed the 'lock' button. The hatch seemed to close normally, I didn't touch anything else. Got in the car and pressed 'start'. Nothing happened, and a car diagram came up on the dash, with a red line across the hatch. I got out of the car, this time a kick didn't work, so squeezed the handle and lifted, after a bit the car took over and the hatch rose. I gave it a few seconds and pressed 'lock' again. The thing closed, and after getting back in, the car started normally.

I really do like the car, though I'm not impressed with Sandown's rattle curing failure, so when I deliver it to them on Tuesday, I'm going to stamp my foot very politely, and insist on speaking to the Service Manager. As I said before, watch this space.

 

[Rob7seven]

You'll all be pleased to know that my little B seems to be fully fit and healthy again. I took it in to Sandown last Tuesday, and collected it the next day. When I phoned to book the car in, I got the impression that they had little idea what the problem was, but once they had the car, they ran through all the software tests, and found a fault they hadn't come across before in an electronic module that sends information to some central control device. The fault must have occurred after I'd had the car for a month or two, as that's when the problems started. Please don't run away with the idea that I know what I'm talking about here, my contact Holly in the Service Department went to some lengths on Tuesday evening, and again when I saw her the next day, to tell me what the problem was, but while she was explaining patiently about electronic modules and a succession of components, all with different three letter acronyms, I expect she could see that I was barely following her explanation, I have an analog brain rather than a digital one, I think she was telling me that this naughty module thingy kept telling the central computer that the hatch as open when it was shut, and vice versa. She told me that there were 46 of these module things in the car, so as you'll probably realise, the scope for electronic problems is huge, and will almost certainly get worse throughout any car's life, something for every one of us to worry about as our cars age, so not exactly progress is it? Bad news for the less well equipped independents that many of us rely on, and I think that Sandown's labour charge is something over £200 an hour already.

 

[Rob7seven]

Oh dear, it seems I spoke too soon. Sandown returned my car on 16/10 after keeping it overnight, apparently confident that they'd identified the problem and fixed it. They said they were sure that the opening hatch fault wouldn't show its naughty little face again, and I could leave the car securely locked overnight again without a care in the World, but just two days ago, it happened again, exactly the same as before. Anne had to stretch to reach the hatch to pull it back into place, those things are heavy, the normal power assist is really needed. The rest of the car remained locked, it didn't give the usual toot, but the lights flashed, at no time has the alarm been triggered. Sandown are having it back on Friday, but it's hard to see what more they could do. A quick Google revealed that opening boot/hatches is far from an unusual problem with various Mercedes models, there were several pages detailing similar faults. Last time Holly told me that they'd applied a software update which she seemed to think should cure the fault, but clearly not. Wish them and me better luck next time they have the car back on 01/11.

 

[Rob7seven]

Don't know if anyone is still interested in this, but to update the story, here's the latest installment. I delivered my B to the Dealer last Friday, and got it back a couple of hours ago, so Tuesday. Sandown can't reproduce the fault, it won't misbehave to order. I think they're doing their best, they checked everything yet again and did more software updates, so we'll just have to wait and see. I took delivery at the end of June, and this is the fifth time it's been back, just a couple of rattles the first two times, the rest the hatchback problem. The only good news is that each time it's returned it comes after a full valet, absolutely spotless, just as it left their showroom. I haven't had to wash or vacuum it myself once.

 

[EmilysDad]

could it be a faulty key that's telling the tailgate to open?

 

[rf065]

could it be a faulty key that's telling the tailgate to open?

OP's been told twice in this thread to use a Faraday pouch, I don't believe he's listened to that advice, so will be unable to tell you if a faulty key is causing this.

 

[Rob7seven]

OP's been told twice in this thread to use a Faraday pouch, I don't believe he's listened to that advice, so will be unable to tell you if a faulty key is causing this.

No, as I've already made clear it's not a key problem, Sandown never thought it was. They had both keys this time, sent a very pleasant young woman along to my house to collect the spare. They've both been checked and rechecked and then reprogrammed as a precaution, along with a second full software update, and they've agreed that it's nothing to do with the keys as far as it's possible to tell.

 

[rf065]

No, as I've already made clear it's not a key problem, Sandown never thought it was. They had both keys this time, sent a very pleasant young woman along to my house to collect the spare. They've both been checked and rechecked and then reprogrammed as a precaution, along with a second full software update, and they've agreed that it's nothing to do with the keys as far as it's possible to tell.

Your faith in Mercedes dealerships is admirable, but for £5 or £10, I'd get a couple of Faraday pouches and prove it for myself before I'd take their word for it.

 

[sonic]

Your faith in Mercedes dealerships is admirable, but for £5 or £10, I'd get a couple of Faraday pouches and prove it for myself before I'd take their word for it.

Just stick you keys in your microwave it is a faraday cage. But dont turn it on!

 

[mioba]

Your faith in Mercedes dealerships is admirable, but for £5 or £10, I'd get a couple of Faraday pouches and prove it for myself before I'd take their word for it.

That.
You have to be very careful with these keyless go crap.
Many stories of cars being pinched easily this way.
Could well be some naughty people hanging around your car at night trying it on.

 

[KennyN]

They've both been checked and rechecked and then reprogrammed as a precaution, along with a second full software update, and they've agreed that it's nothing to do with the keys as far as it's possible to tell.

I believe the keys go to sleep if not used within a certain time , would the vibration of someone walking past their location be enough to wake them up ?

How did the dealership check and recheck the keys - did someone sit and monitor the vehicle and keys for hours on end to see if they started to transmit ?

I would take the dealerships diagnosis with a pinch of salt , regardless of how pleasant the young key lady was.

For the sake of £10 i would get a couple of pouches as it would absolutely rule out any issues with the potentially faulty key(s)

K