So, I've had my car off the road for a couple weeks and I accidentally let the battery discharge to the point where even the little LED that flashes on the dash quit blinking. I did the following in this order:

1. I hooked a 1.5A trickle charger to the jump terminals over night. During the time the charger was hooked up, several of the dash indicator lights were glowing very slightly.

2. In the morning, the charger indicated fully charged so I removed the connections and tried to unlock the door with the remote. Not working. I opened the door, no interior light.

3. Next, I unhooked the battery and attached the charger directly to it and ran it for 6 hours, after which time it indicated fully charged. Still no remote unlock, no interior lights. I tried the key in the ignition and the column unlocked but when I turned the key, the alarm went off and would not stop until I removed the battery terminal.

4. I reconnected the battery terminal and now the column doesn't unlock when I insert the key and nothing else works. The only thing I notice that works is the little LED on the dash will flash when I lock the door with the key and it quits when I unlock the door. Nothing else on the car works or shows any sign of electrical life.

My question is: Is there a reset procedure for this? If the alarm is set off, is there a waiting period before the things will work again?

I have not tested the voltage yet at the battery but I'll do that tomorrow.

Thanks.

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

The Mercedes security system has fully engaged.

It is in disabler mode.

The vehicle needs the MB dealer to unlock the system.
Some dealers have mobile technicians available to fix this at your location.

Or you can buy the Mercedes STAR diagnostic tool:
A China illegal version (that 50/50 odds may work) is $500.00 - $3,000.00 USD.
The legal authorized Mercedes STAR diagnostic tool is a yearly subscription of roughly $28,000.00 USD.

If I recall correctly, there is one more level to that security system = if it goes into stolen mode = not even the dealer will be able to make the car function, without replacing module$.........

.

__________________
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Dynamometer.
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Technical Quality Auditor.
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1985 300SD
1983 300D
2003 Volvo V70

https://www.boldegoist.com/

One possibility that came to mind was that the battery charger was giving a false reading. Not that the battery charger is faulty, but rather that the battery is so discharged, it won't accept a charge. This is what I am finding with my tractor battery on my Cub Cadet when the battery is kaput. Nothing was wrong with my battery charger. Just an idea.

__________________
'06 E320 CDI
'17 Corvette Stingray Vert

Usually just taking off the terminals for a bit, and clamping them back down does the trick to reset most faults. It sounds like though, it is in safe mode. You would need STAR for this to unlock it.

Hopefully the dealer provides this roadside service free of charge for making such a pos of a system.

Does the key in the trunk now work to get the alarm theft system disengaged like on teh old w124s?

Am i understanding correctly that if i take the battery out of my w210 e300D for a week and put it back it it is going to think my car has been stolen and disable it?

__________________
What Would Rudolph Do?
1975 300D, 1975 240D, 1985 300SD, 1997 300D, 2005 E320 , 2006 Toyota Prius

Wow....this is a bit disconcerting...to think that simply a drained battery could create this kind of a headache.

__________________
14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 158k miles
06 E320 CDI "Rutherford", Black on Tan, 177k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 144k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 72k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

OK, thanks. The car is sitting on my carrier from a previous catastrophic failure so It's not a big deal to haul it down and have it reset.

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

Make sure the battery is a good one. I am not sure I've seen where you have verified it is a good one.

__________________
Jim

Does your car have a second battery like the CDI's for backup of critical data in case the main battery fails? If not, please add one.

__________________
85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

What is the story on that failure??

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

I think would be pretty challenging to retrofit because critical circuits could have to be separated into a different circuit that could be passed over to the second battery electronically when the primary got too low. I would be interested in thoughts on how it could be done though.

This is correct, it seems like the small charger doesn't really have the power to bring back the battery from such a low charge state. I'm going to try hooking my big charger to it this evening and check the results tomorrow morning.

Imagine the automotive equivalent of an aortic aneurism but that's a story for another thread. I have pictures too!

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

Maybe easier said than done.

Identify the critical circuit and isolate if necessary.

Determine it's power requirement and choose a suitable backup battery.

Use 2 isolation diodes which powers the critical circuit in parallel with the main battery.

When the main battery dies, the backup battery continues to power the critical circuit.

__________________
85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Diode isolation would separate the two batteries, we call that a "best battery selector" at work. Problem is that you also have to figure out how to keep the aux battery charged. They make a device for travel trailers that does this function.

That whole adventure scares me, about 2 weeks ago my W210 battery was getting weak. No problem, I thought. I pulled out the battery at probably 8 am, threw it in the back of the ML, ran a bunch of errands, and finally got back to installing it in the car about 5 pm. Luckily for me the car started normally and all I had to do was re-sync the windows and sunroof and put the CODE back in the radio.

If I had to do it now that I know about your situation, I would have set the battery from my 124 in the battery well and hooked it up, just to keep the electronics happy in the W210. Scary stuff that the car can lock itself up just from lack of power. Or ran jumper cables between the 2 cars.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

If your battery was that discharged, I cannot see how a 1.5 amp trickle charger could bring it back to a fully charged state overnight. I would definitely double check the state of the battery under load conditions. You could have a bad cell that will not show up until placed under load. Good luck

__________________
96 E300d

I don't really understand what has gone on here. Surely disconnecting the battery wouldn't cause all of this trouble with the anti-theft device?

If it was so important (to allways have power) I'd imagine that there must be a back up battery like there is on a computer - these used to be called CMOS batteries - they'd keep basic things like the clock running whilst the computer was switched off.

Shame there isn't an online manual for the W210 I'd be interested in reading up on it. A generation earlier W201 / W124 - disconnecting the battery is a great way of clearing fault codes!

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!