I'm new on this forum and would appreciate any advise you could give me. I have a beautiful 97 E420 with just over 90.000 km. on it. One hot day last summer, 35C. I filled the gas tank at an Esso station then went for lunch nearby. After about half an hour the car wouldn't start but was cranking over just fine. This situation continued so i called for a tow before the battery went flat. I removed the filler cap to check for vapor lock. At the dealership a few mechanics looked under the hood for quite some time then I was informed that they could find nothing wrong. At this time they told me it could be the electronic control unit which would cost around $5,000. I was told that because I put so few miles on the car that I should put a charger on the battery to top it up regularly. Up till this point I had no problems with the battery. I was very concerned with the car's reliability and asked what i should do if this ever happened again. I was advised to disconnect the battery to reset the control unit. This was all they had done and the car was running fine. The the outside temperature had dropped to around 30C by this time. i WAS CHARGED $400 for their efforts and drove home.
The following week the car wouldn't start in my garage because the battery was flat. the engine wouldn't turn over so I purchased a new Delco battery After finding out what the dealer wanted for a Mercedes one. They offered me an aftermarket brand which was still twice the price of the heavy duty Delco so the choice was easy. Things went well for a few weeks but soon this battery began to loose it's charge if the car sat for a few days. I noticed the interior door lights were staying on sometimes after the doors were closed and would go out 10 minutes later. I pulled the trunk light bulb out in case it was the culprit but after about two weeks the battery was losing charge again. If I disconnect the battery it holds the charge fine so that's not the problem.
Yesterday the interior door lights remained on when I drove the car and didn't go off after 10 minutes. I checked the switch on the overhead panel but the lights would not go off. All the doors and trunk lid were closed properly.
The only thing electrically I have changed on this car since I purchased it is a MB Alpine audio 10 CD player from Germany which appears to work perfectly.
Sorry for the long story but I am stumped and would really appreciate any advice. I love this car but I have problems trusting the dealership! Thank you for any help.

 

Find a good independent german car repair shop. Ask around. A friend or business associate's recommendation is usually the best way to go. If you let the "new" shop know that your friend sent you, they may be less inclined to gouge you for fear of losing more than one customer. Just a thought. Sorry about your issues.... they sound quite involved.

 

Thanks for the advice Scuddog. I am looking for a place like that now. Yesterday I removed the fuse which powers the interior lights, so that might solve the problem for now. I am thinking it might be a faulty three way switch in the overhead panel. Only time will tell!