key recognition problem?

MarkyBoy

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Hi all, wonder if anyone can help isolate a starting problem with a 1998 C250TD.

The problem started about 6 weeks ago, when turning the ignition key the engine just goes 'clunk' it doesn't attempt to turn over, you try a few times and the engine just clunks repeatedly, then after a few attempts it will turn over without starting. Then if you remove the key and try again it will start normally. After a week or so, I switched to the spare key and the problem disappeared. BUT after a couple of weeks the problem exists with the spare key now as well and is worse than ever!

I have checked the battery and had the starter motor tested and all is ok with those, so I wonder if the problem is that the key is not being 'recognised' or something... The batteries in the keys are only a couple of years old, but perhaps that's an issue? Any ideas how I can diagnose and isolate what the problem is?
 

grahamcol

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Batteries are only "a couple of years old" suggests they mau need replacements. Worth a try. However, I'm not certain this will be the root cause of the problem. I would say that after a couple of years the batteries are very likely well past their best. Good luck
 
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MarkyBoy

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Don't know if this is connected or not, but the windows do not 'latch' on the switches until the car is running (and key is recognised?) after which they will work fine???!!
 

drmw

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M6 Cab - prior to that, SL63 AMG, A-M V8 Vantage, SL55, SL500 and many more
for the sake of a fiver, I would change the batteries - 2 years isn't too bad depending on use.
 
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MarkyBoy

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for the sake of a fiver, I would change the batteries - 2 years isn't too bad depending on use.


Yes, I'm going to get some batteries tomorrow but would they really cause this kind of problems? I just read you could start the car without any batteries in the key?
 

Mark@RMK

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Batteries only work the locking part of the key..

It could be the keys but if they turn and the start clunks then all the authorisations are being given by the EIS/ECU to start.
 

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