Phoenix405

Hey guys I finally picked up my first W220 and I've been working through the problems to get it back on the road. I'm a bit stumped at the moment as the current problem I've come across is an over-heating battery. During regular operation the battery gets very hot, hisses and smells horrible. It definitely scared me a bit when I figured out where the hissing was coming from and it has since been parked due to fear of a fire. The previous owner had stored the car for about a year and the battery was dead, couldn't say how long it sat dead for. Perhaps it harmed the health of the battery to a point it no longer functions as it should.

With the car off the battery voltage reads 12.1V and while running the voltage reads 13.2v. 13.2v doesn't seem like it would be enough juice to get the battery hot enough to boil.

Could the alternator or voltage regulator be going bad? Am I looking too far into things and I just have a bad battery, would love to hear y'alls insight.

Thanks for your time guys.

tim687

How old is the battery?

Hissing batteries usually mean that there is a lot of sulfation occurring inside of the battery.
So it should be replaced

ChrisHimself

Batteries cooked, you can't leave batteries completely discharged, it permanently damages them the longer it stays that way and it hurts the alternator and starter to try to keep using it. I see this weekly. Not a Mercedes exclusive thing. Switch to AGM so you have a safer, more reliable battery as well. Don't overthink it. One thing at a time.

Phoenix405

Great news guys, putting a fresh battery solved all of the overheating problems.

The battery tester showed 350 CCA on the old battery and said it was no good. To answer your question Tim the date code on the battery was 04/2018.

Only problem now is the sunroof will not close , it worked fine before the battery swap so maybe it just needs a reset? On a positive note the car runs great and I was finally able to go on my first real ride in it!

Thanks ChrisHimself and tim687

ChrisHimself

it might have to be re-sync'ed/reset there are youtube guides

wallyp

Push and hold the sunroof switch in the open position until it opens completely, plus three or four seconds.

Push and hold the sunroof switch in the close position until it closes completely, plus three or four seconds.

Phoenix405

Hey guys I was unable to get the sunroof to close with the reset method. I ended up manually closing it with an allen key due to an impending storm. Once the weather cleared up I manually opened the sunroof all the way and tried using the switch and the sunroof would only close regardless of which direction the switch was pushed. Currently the sunroof will only tilt up in the rear and close, it will not slide back regardless of what I try.

wallyp

Did the open and close manual operation require a lot of effort? It is not unusual for the tracks to need cleaning and lubricating.

tusabes

If you can manually close it, just close it and don’t use it again.

wallyp

I don't think that I have ever even tried to open the sunroof in my S500.

Phoenix405

I was only able to regain tilt up and down functionality to the sunroof. So I'll probably leave it as is for the time being