Ignition key won't turn

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New Member
Mar 20, 2017
C270 Avantgarde
Morning All, new fish here.

Tremendous resource this site, wish I'd thought to look for it 5 years ago!

I've a gremlin with an intermittent twist that might just cause heart failure if I cant get some quality advice...hence my joining the forum.

I have an 02 plate C270 estate which has developed a bit of a teaser! Drove the lad to the station the other day and the dash display including speedo, computer, indicators etc went completely blank. Engine unaffected and radio still worked. Obviously electrical I figured (and my ignorance of sophisticated car electronics is almost complete). By the time I arrived home some 15 minutes later, its back.

Next time I come to take the car out, can't turn the ignition key in the barrel of the ignition. Central locking works but the key simply wont turn. next day, it works again!! I take it to my local (non Mercedes) village mechanic, a good bloke but without the sophisticated diagnostic tools of a main Mercedes dealer. He does have some diagnostic setup and no codes are evident, but then it's working at this time anyway. I get it home, it breaks again. Over the following 2 days it breaks, it works, it breaks, it works. Classic intermittent fault. I'm told it's either the key electronics or the EIS electronics and even in a main Merc dealer with appropriate diagnostics, they cant tell which. Thus usual method of elimination is to try your spare key, if that works, bingo, it's the primary key at fault. However, if you dropped your key into the sea while wading at chest height bass fishing, it often doesn't work any more!! (Right about now you may be regretting me joining the forum).

Bottom line, this car is on it's last legs but I need to keep it running for the rest of this year without spending best part of a grand on ignition bugs. My assumption, with little car knowledge but a healthy dose of logic is as follows:

It's most likely the EIS because otherwise why would the dash have gone dark on me? A faulty key can't cause that can it? What I don't want to do is order a new EIS only to fund I've spent 3-£500 on a "mindless parts swap" and still have the pleasure of the fault.

Whats niggling me is some geezer in the trade mentioned that it's likely to be the EIS but it's not 100% sure. Is it possible to get to be 100% sure without selling a kidney to find out (ie a Merc main dealer)?

Your help is appreciated.

PS the reason I'm being as tight as a mermaids brassier is that my business has just failed after spending 2 years nursing my wife back to health from cancer whilst simultaneously doing the same with my young son who has a rare bone disease and has had 15 operations to try and repair his leg at the Royal national Orthopaedic Hospital in Stanmore (which is miles from where I live by the way). It hasn't been a joyful 2 years! But if I can fix this sodding car I'll be happy man!
That's a helpful response, many thanks. That team looks very useful indeed. I'll call them Monday.

Can anyone respond to the issue of whether or not it can be ruled that given the dash going dark symptom, that is a 100% certainty that the cause is the EIS? Again, this is to try and avoid the mindless parts swapping syndrome. Could any other electrical fault cause the dash to intermittently fail (speedo, computer, indicators etc but not the radio)?
Allied to sending the EIS to the team mentioned above, does anyone know if it's a simple job to remove the EIS unit ones-self? (For posting for repair).
There are several YouTube videos on EIS removal- most are LHD but principles should be the same. There are several companies that offer EIS repair service if you do a search. I can't recommend any particular one as I have never used one myself. Anyone worth doing business with should be able to advise you on the unit removal? Perhaps another forum member who has availed themselves of this type of repair might comment?
Well on my w221 it is very easy to remove at the right end of the dash there is a cover which you can remove this exposes a grid of fuses,but there is a fastening that you undo then it swings out of the way and then you can access EIS,with regard everything going off on the dash,but the engine still running fine,I had that on a company vectra a few years ago,the stealers wanted to put a whole new dash in ,but all you had to do was disconnect the battery for about 20 mins and then everything was back to normal.
It's your key if you dropped it in the sea!!

Thanks to the two recommendations above!
It's your key if you dropped it in the sea!!

Thanks to the two recommendations above!

My spare key got dropped in the sea, now I only have the one...hence I cant test using the spare.
You could go to eBay or local scrap yard get a set from same model and engine size scrapped car

Get a complete set
Steering lock

Fit to your car it's all plug and play
Only problem I see is steering lock of key won't turn but can be done
Thanks again for the help chaps, most appreciated.

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