2001 Other Mercedes Benz Models Key wont turn, wont start th

NEURO

MEMBER
2001 MERCEDES BENZ
6 CYL
2WD
AUTOMATIC
140,000 MILES

It seems that I have a strange problem.
My benz is a w203 2001 c240 144.000km
After some 3 month rest in my native small town (no benz workshop in 150km distance), I deceided to take it for a drive.
Damn I should have asked someone to start the engine for a ride once in a while, now I have a dead battery.

"Hey dude, big deal" my friend said, "let me elp you with my wires"
And. Nothing happend.
The remote control didn't work!
No opening/closing doors and no sucking sound when I place it to the ignition.
Lights, radio work fine.

(he used the right polarities from his benz and we left the interconnection running for some 10 minutes)

Off for the local auto accessories store. First 140 Euro for a sealed battery
(mine was 12V 100AH and they sold me an equivalent 95AH. Or something)

Installed. But. Nothing again!
Checked the fuses in the back. Nothing

Damn. In the afternoon, 8-9 hours later, (it was dark already) simply went to disconnect the wires so that the new battery wont worn off.

MAGICALLY everyhing is ok, the remote is active again, I can start the engine, reset the windows&roof, the ESP. An take it for a ride!
(Ok, I toook it for 3 rides of 5km each)
Great that was it, no big problems here.

Exact same story at the second attempt using my car, after one week.
"Thanks god it started, tomorrow first thing I drive it to a specialist".

Yeah I wasn't that lucky the thind time never came.
The next day I tried everything from the begining, checking the fuses again one by one. No joy.

Tried the spare key. Same story. They both work good I think.
The IR works and the idle flashing light of the cd-player inside the car stops flashing for a moment when I use the keys (receiving something I guess?).
I even changed the batteries.
Any thoughts?

1 Reply

GFIMOTORCARS

MECHANIC
673 POSTS

This may be an amperage draw from your seat control modules. These are notorious for killing batteries in 203 body style C classes. This will continue to kill batteries as it slowly draws the amperage out of the battery due to the control modules not fully turning off after the vehicle is turned off. These are black boxes located directly under the drivers and passanger seats. You can disconnect the seat modules and see if this prevents a new battery from going dead over night. THe connectors on the modules are a little tricky but they will slide to one side to disconnect.