As part of the common ESL problem of the car not starting as a, one hopes German ESL motor lost the carbon brushes and a Chinese US$5 motor got put in by Australian ECU Repair, the ESL and the ignition lock (EIS) and key got sent off to them and they fixed the ESL for $450. Sometimes the key itself gets very hot once I finish driving and pull the key out. That is intermittent - normal temp. yesterday.

The problem must be the EIS and that is a worry as a Merc stealership is charging a king's ransom for lost keys and I will probably not only need a new EIS, but also a new key. Why is the EIS getting so hot, that it transmits heat to the key? As a master switch it is obviously transmitting lots of Amps (?) and due to a fault becomes hot. Is that also the reason for battery problems, which I had put down to "parasitic draw"?? Suggestion: Heating the EIS during driving reduces the Amps going into the battery? Voltage during driving is 13.7V, but perhaps not too many Amps are going in?

Or does the EIS only carry a low-Amp current to a relay, but then it should not get hot? Too many questions, so little time! Thanks.

P.S.: My belief in German quality has been severely dented since the ESL disaster as the car was stuck under a River Gum, which likes dropping massive branches, so I had to build a roof over the Merc for the repair. Two Perth stealerships did not change the fuel filter nor the auto gear box oil at the recommended 60k and 120k km, so the service also stinks like the gear oil I pumped out. The filter was contaminated as I cut it open to look at it. They may just look at the fuel flow on the scanner and if it is in range, forget the change. The web is full of complaints due to battery problems possibly due to parasitic draw.

 

EIS getting hot is an unusual failure. Maybe scan for codes? Some stored and active codes don’t turn on the CEL as that’s more related to emissions issues. Correlating that to battery drain makes sense, though.

As an FYI, I don’t think the EIS handles much current at all. It just talks to the CANBUS (controller area network bus) as part of the drive authorization system (DAS) to tell the system that the right key is in and what position it’s in.

Since you don’t need to know it to get your problem solved, I won’t go deeper into the DAS unless you insist. It’s described in detail in a number of forums and threads here anyway.

 

I can tell you this for a fact, because it happened to me, if you have an ESL emulator and you need to have the transmission conductor plate replaced, you will not be able to fully code the new conductor plate. Two VERY good transmission shops were unable to do the coding and my car had to be flat-bedded to a Mercedes dealership. They were unable to code the conductor plate as well, until itbwas the ESL emulator causing the problem. They installedcan OEM ESL and, bingo, they were able to code the conductor plate.