Bizarre Problem with my 2004 C240 Mercedes
05-27-2013, 11:53 PM
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Mercedes C240
Bizarre Problem with my 2004 C240 Mercedes
I have been racking my brain trying to figure out what is wrong with this car. About 50% of the time I will start the car and almost no electronics will work. Speedometer, windows, gas gauge, etc do not function at all. Radio still works fine. If I start the car and they do not work, if I turn it off and try again sometimes everything will work fine sometimes I have to try 4-5 times and then everything functions. I have been told it could be a Rear Sam, a bad Key, or the EIS. Does anyone have some pointers on how to figure out which or do I just need to start paying the dealer $$$. Thanks!
05-31-2013, 05:39 PM
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C230 MERCEDES BENZ
KEY PROBLEM
It maybe be a low battery on the fob. If that doesn't work. If you have a spare, try that first before ordering a new key. I had the same problem with my 2004 C230 until one day the key would not turn at all. I had it towed to the dealer and they said it was probably the smart key that went bad. I didnt have a spare so I had to order a new one and have it programmed ($350). When the key came in it still would not start the car so the dealer said it was the EIS. I had that replaced for ($1200). I just received a call and they are saying that didn't work they need to run further tests. I will keep you posted once I find a solution.
06-01-2013, 04:01 AM
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2005 C Wagon (No snickering please!)
In your case I suspect the super cheap relays that supply power to different consumers in the car. The EIS signals the SAM's on the CANbus that the key is good and the boss wants to go somewhere. The SAM pulls the relay coil to ground and the swinger is pulled toward the coil magnetically. A contact on the swinger is slapped against the stationary contact and the connection is made. Every time the relay operates a small spark causes carbon to form, and even melts or wears the contact. The carbon or oxidized surface is an insulator and the connection may or may not be closed. Slap it again and it is fine.
Terminal 15R is the name applied to this circuit. There are several relays to check. The rear SAM has two. Each relay has an address. Address B and F are of interest to you. The front SAM has address M and P that are of interest to you.
Location and map are contained in this thread:
https://mbworld.org/forums/c-class-w...gram-w203.html
Some relays can have the cover removed and visually inspect the contacts. These relays use faston terminals that can oxidize as well. Simple removal and reinserting can wipe the terminals.
Terminal 15R is the name applied to this circuit. There are several relays to check. The rear SAM has two. Each relay has an address. Address B and F are of interest to you. The front SAM has address M and P that are of interest to you.
Location and map are contained in this thread:
https://mbworld.org/forums/c-class-w...gram-w203.html
Some relays can have the cover removed and visually inspect the contacts. These relays use faston terminals that can oxidize as well. Simple removal and reinserting can wipe the terminals.
