After sitting overnight, our 1999 E320 we have to remove the key and re-insert it before cranking. Is this normal?? Also, how close should you have to be to the car for tha key remote to unlock the door?? Thanks!!

Do you leave the key in the ignition overnight??

The key has 2 types of unlocking signals...radio frequency range should be 25+- feet.

The infrared signal range is 3-4 feet & must be aimed at receiver.

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Yes we do leave the key in the ignition overnight since it is garaged. As for unlocking, can you switch from infrared to rf and if so, how?? Thanks!!

Should NEVER leave a "smart key" in the ignition, that can RUIN the $200+ key.

You can leave it in the console w/o any negative effect though.

Key transmits both signals every time you press any of the buttons.

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MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

Okay, I did not know that about the key. But why do I have to be within about 4-5 feet of the door for it to unlock them?? That makes it not much better than having to insert the key to unlock. Thanks.

BTW Just replaced my key yesterday at, of course dealer only. COST total $ 235.00 USD programmed.

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M.B. Doc said the key works at 25 feet. I would say my range is 10 to 15 feet but my battery is not new. The IR function is for the express window down feature.

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

1st question?? does the key have new batteries? 2nd, do you have more than 1 key & do both keys do the same thing?

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MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

No and yes. I tried the other remote and it works from approximately 20 feet. Next time we are near a MB dealer I will stop in and see about getting a new battery. Thanks!!

No need to go to the MB dealer. It uses a very common watch/electronics battery - a CR2025 if my memory is any good (usually isn't). Instructions for changing the battery are included in the owners manual.

Okay, can anyone tell me if JC is right about the battery number for the electronic key?? Thanks!!