Intermittent SLK 171 ignition problem

[topradio]

Hi all & thanks for such a great informative site. This is my first post but I hope to be able to contribute more over time.

My o/h has owned a 2008 R171 SLK280 from new. when it was about 3 months old it developed a problem where the smart key would remotely unlock the doors but when inserted in the ignition it was not recognised. Normally there is a buzzing sound (steering lock?) and the displays light up but in this case this does not happen and the key obviously won't turn. As the car was under warranty we called out MB support and the chap that came out fixed it and said that he had done a 'hard reset'.

Now it has done the same thing intermittently perhaps 5 or 6 times in the last 8 years and I have simply left it for a few hours and it miraculously works fine. When it happens both keys are affected.

I am an electronics engineer and the fault 'feels' more like a bug rather than hardware. However I have searched a number of forums and can't find anybody reporting exactly the same fault which is surprising as I usually find that most problems like this are common and many people report suffering the same thing.

Has anybody else had this happen and is it a known problem?

Many thanks for your help.

 

[topradio]

Update

I thought I would update you on this problem.

I have left the car for 24 hours but the problem still exists.

Thinking about it, it only happens when the car has been left unused in the garage for perhaps a couple of days and NEVER when out and about. Now the whether is starting to get colder here and the battery is the original one. I measured the battery voltage and it was 11.95 volts which didn't seem bad and when working cranks the car over just fine. I connected up a charger and immediately tried the key in the ignition and hey presto it works!

So its looking like the ignition circuitry is very sensitive to battery voltage and if not tip top it just doesn't recognise the smart key.

Now I would suspect that the smart key and its associated lock are common to a number of MB products and this may be something that other owners may encounter.

 

[NDFR]

My first suggestion is battery, but you should have Star connected and see what error codes you have.

I had a similar problem which ended up being steering lock issues.

 

[topradio]

Thanks for the reply. The car is going for its annual service with Alex Crow in Stowmarket in a few weeks. I will get him to read the codes to see if it throws up anything.

 

[topradio]

Update on the update

OK, so I spoke too soon.

Yesterday I connected a charger and the ignition turned on but I never started the car. I thought I had got to the cause of the problem.

I left the charger connected overnight and this morning tried again while it was still in circuit. This time it was the same as before, the key was not recognised and will not turn however I notice that when the key is inserted there is a faint click from behind the glove box area (immobiliser?) so something is going on.

So its back to the drawing board, it looks like I am going have to get the codes read to see if that throws up anything.

My wife was talking about a new car this year so it looks like it may be sooner than she thought.

I will let you know the outcome.