todthedod

Ok late last night I need to get my car (2012 c63 coupe) about a foot farther in the garage to close the door. Instead of cranking it and waking the neighbors (2nd cat delete and Mike's X-pipe hehehe) I pushed the start button without the brake pressed to put it in neutral which I've done one other time successfully and just used my hulking mass of muscles to push the car in. No problems all good but maybe I forgot to push the button again to turn off. Is this necessary? I know my last car (BMW) would turn it off after a couple of minutes. I'm not sure since this car is new to me.

Get up the next morning, open the unlocked door and quickly realize the battery is dead because of no light or sound or anything. I put a slow charge on it and checked it a few minutes ago and the battery is holding at 11.86v. When I get in the car everything is normal as far as lights and sounds, etc but the display says "don't forget your key" so it's like I just turned the car off. If I try to press the start button I get a "replace key fob battery" no matter which key fob I try even though both were working fine before.

I have one of those battery pack charging thingys that I can connect but it still does the same thing.

I'm thinking maybe whatever I did finally killed the battery. Maybe the battery pack thing isn't strong enough but I figured I'd ask here first before I go get a new battery just in case it's something simple I could try.

realjones88

That's a pretty low voltage. I would try a charger with dusulfator ability to see if it can bring some life back into your battery - I used the Batteryminder 1500.

I killed my battery very dead (like below 10v) and my regular trickle charger couldn't do much with it. The sulfator brought it back to life.

ItalianJoe1

Did you try to use the actual key in the car? Sounds like the keyless go is having a low voltage issue. Pop the button out and put the key in the EIS and try it.

The cars require a good strong battery for everything to work right, but it should still start at 11.9 V, although it will be sluggish.

todthedod

I put a bigger Schumacher (10A) charger on it and it won't go over 11.83v but the charger is really really old so it may not being juicing it up accordingly. I'll try a mack daddy charger tomorrow.

todthedod

You can pop the button out?? LOL Like I said the car is new to me.

todthedod

Well I'll be damned. That worked! Started right up

ItalianJoe1

Happy to help!

Sometimes, the keyless go unit gets itself all riled up and just will not recognize keys or what have you. There are LI documents that say to disconnect the KG module first to reset it when troubleshooting odd or intermittent issues, then update the software. There's something in there that the germans know about but haven't fully fixed, sometimes it just goes stupid.

ItalianJoe1

Because your car had very low voltage but didn't zero out, the module may need to be reset in your case. If you're warranty is still valid and the issue persists, take it in. If not, disconnect the battery, press the brake pedal a couple times, let it sit for a few minutes, then reconnect and see what happens.

INS1GNIA

Check out https://mbworld.org/forums/c-class-w...ts-thread.html to help discover your car some.