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Hello, I am new to the Benz world and have replaced one of my Audis with a 01' C320 and can say I like the car but wholly crap is this a electrical system nightmare!!! Anyway, my son attempted to open the doors this morning with the remote but the locks did not open (about 60 degrees). He was able to open the trunk with the remote and when he hit the lock button the lights blinked and it seemed as if the system was relocking everything.
I have been reading for hours now and have not found anyone who has said the remote works partially. Can anyone tell me if this sounds like the EIS I read about or a remote battery issue or even the main battery or something else. He did not try to open the door by holding the remote close to the IR sensor on both front doors or did he get in to check to see if it starts so I dont have all the diagnostic info needed.

P.S. The remote seems to be completely working now that it is later in the day and the temperature is now in the mid 70's
 

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2002 C240
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I have an 02 C240, bought it used about 8 months ago. The remote door locks would only work occasionally, maybe 1 time out of 20 tries. The car always started fine though. I installed a new battery (Duracell brand) in the key fob but it did not improve. It would only work when I would hold the key less that half an inch from the little black plastic sensor window on the non movable part of the drivers door handle. We ended up using the mechanical key to lock and unlock the doors. About 2 months ago my wife looses the one and only key we had. So I get a replacement key form the local dealership (about $220) and the remote door locks work much better now. It reliably locks and unlocks from about a foot away now. It is way better with the new key. A week later my wife finds the original key so now we have two. I also could experiment with the old vs new to see why one worked well and the other didn't.

I conclude that the IR LED in the original key fob is weak, it just doesn't put out enough IR light to get the door sensor to work reliably. Also maybe the little black sensor window is clouded from age the way plastic headlight lens get or the sensor in the door is weak. Strange thing is I can't see through the black plastic sensor window on the door handle to what is on the other side. It is supposed to be somewhat see thru or is it normal to not be able to see through it at all?
 

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Coupe/Convertible Forums Moderator
CURRENT: 2011 SL550, 2011 C300 FORMER: ML350, CLK550 Cabriolet, C240, ML320, 300TD
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OK, I know there is another thread regarding this same problem, but I'll use this one to explain the system:

SmartKey Functions
 
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