W221 s500 flat battery

[Jumpingjackflash]

My S500 w221 is totally flat. I can open the boot using the manual key. When I lift the boot floor I can see a red cable. Is this the positive cable to charge the battery and where is the earth? How do you trickle charge a flat battery on a w221?

[Scrump]

If it is totally flat then I suspect that you will need a new battery/batteries. They often don’t recover fully after being fully discharged.

The battery cable in the rear may be for a small auxiliary battery, I have no experience on the S class, just know that my E class has the main battery in the engine bay and the auxiliary battery under the boot floor.

[Mogul]

Can’t you enter the cabin with the blade key like this?

https://youtu.be/o9BOQbq9o9I

[Jumpingjackflash]

I can not enter cabin with blade key. I have been unwell for nearly six weeks. The car has not moved. The manual key does not open the drivers door. I can open the boot with the blade key.

[Mogul]

I haven’t tried this myself but here’s another source that suggests that there may be a knack to getting the door to unlock with the blade… (red shoes may help!)

https://mbworld.org/forums/s-class-w221/454703-bat...

[Old Merc]

Jumpingjackflash said:

I can not enter cabin with blade key. I have been unwell for nearly six weeks. The car has not moved. The manual key does not open the drivers door. I can open the boot with the blade key.

I had this on my C270 after time in hospital. I tried and tried with the blade, but no luck, so gave up.
Went back a few days later and it worked. Don’t ask me how and why, but it did. Just keep on trying, maybe some WD40 in the key hole.

[AndrewCrown]

Mogul said:

Can’t you enter the cabin with the blade key like this?

https://youtu.be/o9BOQbq9o9I

This worked on my W221 ….turn the key to the left then you need to yank the door handle ia few times quickly

Edited by AndrewCrown on Monday 22 May 19:56

[Jumpingjackflash]

I GOT IN!!!!

I sprayed WD40 in lock and door handle when trying to open it and the door opened. Thank you

[Mogul]

We all love a happy ending!

[Old Merc]

Jumpingjackflash said:

I GOT IN!!!!

I sprayed WD40 in lock and door handle when trying to open it and the door opened. Thank you

I thought it would work eventually, I bet that blade has not been used for many years.