Hi I am looking for some assistance with some electrical problems my car has been experiencing any help will be greatly appreciated
The problems started a few months ago with the car all of a sudden lowering the passenger window turning on the interior lights and then shouting at me cause the door was open it was however properly closed and if I opened and then closed the door the problem went away, then the traction control would activate for no reason whatsoever I could be doing a constant 60mph on a straight and dry road with no potholes and the TC would bring the car to a halt very violently about the same time my COMAND would reboot its self whenever it felt the need and would take over a minute to change a CD track these problems still continue.
Now yesterday again on a straight level and very flat road the car tells me its out of oil and to stop when I pulled into my office car park I checked for any oil leaking and found nothing so I left it for 30 mins and then used the press R 3 times trick to check the exact oil amount and it said 15.5L but the tank is not that big so I left it again for half an hour and tried again and it said 7.4L that seems like the correct reading to me however my headlights have decided that they are not needed and refuse to function and the windows will not fully close, does this sound like a computer fault to you guys as I plan on having the dealer recode every single module in the car to the latest software versions before I will accept it back.
Sorry about the long post and thanks in advance for any help
Dan

 

Hi,

Are you able to check the oil level manually under the bonnet on a SLK55. If so I would do so.

Have you spilt any beverage inside the car somewhere. Do you use a car wash regularly?

I don't understand your sentence....
"I could be doing a constant 60mph on a straight and dry road with no potholes and the TC would bring the car to a halt very violently"
Why TC = Traction Control??

Since this is a new car I suggest you get a MAIN MB dealer to get it sorted.

Stuart

 

Hi Stuart
By TC i mean traction control and the problem was located the cause was water in the engine bay fuse box caused by a fault seal the water damaging and then finally destroying the ecu and caused severe damage to other electrical components in the car causing the problems i have been experencing lucky for me the only time the box has been opened was by the dealer so the cost of the new electrical system is being taken by them.

Just to answer your questions i dont think there is a dipstick in the car at least not that i am aware of (it would be very handy to have one as a backup tho), i dont use car washes as they scrath the car its silver to they show real easy and i have never spilt anything in the car i would kill myself if i did.

Its just lucky that the car did not die when i was driving the thing because the steering locks and that could make for an intresting ride!

Thanks for the reply

Dan

 

Hi,

Glad you got it sorted.

My question about car wash and beverage were aimed at determining whether water had infiltrated the works. Your symptoms were very "water ingress" like since so many systems were acting strangely.

Water acts as a conductor between the various wires on the printed circuit boars in the computers, connectors etc and the strangest things can happen. All systems are designed to ensure that in the event of a circuit malfunction the result will "FAIL SAFE" or at least that is the goal!

The TC is linked to the brakes (to stop individual wheels spinning) but i'm surprised that they actually applied and stopped the car. (I don't doubt your word)
The failure mode was obviously not completely thought thru although brakes are problematic. Sometimes you want them to be applied in the event of a failure, othertimes (like this) not.

Out of interest how did the water get in? The electrics box is pretty well sealed and drained. Its important that this is understood otherwise you will have a repeat problem in the future.

For info you will NOT lose your steering if you lose your engine. The steering will go HEAVY but it will still work (However the heaviness will come as a great surprise). The only thing that will actually lock the steering (prevent it from turning) is engagement of the the steering lock.

Stuart

 

Hi Stuart,

I find it amazing that you without even seeing the car go straight to the problem and it took my dealer days even with a pond in the fuse box, thanks for your explanation of the effect and the cars reactions to water ingress it was a better response than the dealers.

The TC has activated for no apparent reason a few times now and i am just as surprised as you are of the reaction to the failure and the way to clear the fault i.e remove key wait for computers to power off and restart it can be very interesting while sitting on a busy road!

The water was allowed into the box because when the dealer removed the cover to replace a blown headlamp fuse the did not seat it correctly so the one side was slightly raised and the water ran down one of the rubber tubes containing the wires and into the box travelled along the now exposed wires and onto the fuses and the ecu i was unaware that there was a box drain so i will have them take a look at it as it must be clogged or something.

I understand that with the loss of the engine the power steering will also go i have been unlucky enough to experience that on another car what was worrying me was that the car totally shuts down like removing the key and when the key gets removed the steering locks and i was worried that it might decide to lock the steering but hopefully now since they know what the problem is it should be fixed before i drive it again.

Thank you for the reply it was very informative i will see if i can get a pic of the box now while its still full of water and post it up for you to have a look at.

Dan

 

Hi Dan,

I could be wrong about a drain since no water is supposed to get into the box. However as a designer myself I would ensure that there was one just in case. My experience is on the previous R170 model rather than your R171 which had a cooling blower in the bottom of the box to circulate air. Not sure about R171.

Was this a main dealer?

If I were you I would get some sort of agreement from them that if you get problems in the future they are liable since electrics give very difficult to solve problems once they have got wet and corroded. The fact that yours got wet albeit not over a prolonged period (thus reducing the likely hood of corrosion) will have done nothing to help long term reliability. How are they going to dry it out? Putting the cover back on without ensuring it is 100% dry will tend to create a micro climate which will speed corrosion of terminals etc.

Modern electronics have many tests which are conducted during startup (Booting - in computer speak). These checks ensure that the actual values from sensors lie within specified ranges thus trying to spot problem before they become apparent. These tests are often so sensitive that just restarting can appear to solve the problem. However there's no smoke without fire and even if the warning light goes off after a restart doesn't mean that there is nothing wrong. It will usually come back.

Quote: "The power steer goes".
If the engine stops or the power steer belt breaks you end up with no Power Assistance. The steering is still connected and works fines so long as you exert extra effort. The transition between having power and not having it, is however quite worrying, It may feel as though it has locked but it won't have.

The latest Mercedes have "Brake by Wire". If the electrics go customers complain (very vociferously) they have no brakes. They do have brakes since there is an unassisted back up system that doesn't require electrics. However the effort required is a problem once your brain has become use to assisted effort levels.

I hope you won't have problems in the future but this sort of failure (negligence) is bad news.

Stuart

 

Hi Stuart

thanks for the reply i asked the dealer about the drain and they said there was not one in the box as no water was meant to get in but as you point out it would make sense to include one, it was a main dealer and while some of the service advisers had there heads up there asses as in most places there are good ones and i was lucky the last SA to deal with my car since it has been in the dealer has been very helpful.

I have an agreement with them that any electrical problem is there problem warranty or not, to dry it out they removed every component then from what i understand took the components to bits allowing them to dry out of the car they said that they have checked all the terminals and no corrosion is visible and the box is bone dry now.

Some of the sensor tests where failing so they have replaced those sensors they all seemed unrelated to each other of they put it down to them being shorted out and i have now got an OBDII tester so at the first sign of the EML light it will be plugged in, i tried to get a picture of the box but when i got back in there it had been removed and there was not really anything to see.

I completely agree that this type of failure is very bad news and just to complete the saga i mentioned to them that the rear speakers have never worked and since it was with them could they check them out first they found that the central gateway had not been correctly coded so they fixed that but the speakers where still dead so when they took off the trim the speaker cables where there but the speakers them selfs had not been installed so i am getting the harmon kardon upgrade for free now so i did not bother to shout at them for it however giving free upgrades is hardly something they should be proud of as they should get it right in the first place

Thanks very much for your replies

Dan

 

Happy Motoring! Mine are going strong at 100k+.
Stuart.

 

Thank you very much