Heres a couple of reasons why I'm an idiot. I own a SL500 convertible and live in Washington state, where it rains constantly. I also don't have a garage. Thirdly, I hardly ever drive this thing.

I have a 2003 SL500 (R230) that mostly sits outside. I let the engine run every weekend for a while, but I don't always take it out. Today, I was going to drive it a bit, when I realized that the shifter was stuck in Park. Well, ****, I thought. I did some research and narrowed it down to either being low voltage or a bad brake light switch. I just purchased a new brake light switch to be delivered just in case, so we will see.

The entire time I'm inside doing my research and ordering parts, I have the car idling outside my window, hoping it may charge itself back up after a while of idling. Suddenly, I notice something out the corner of my eye.

The tail lights suddenly start flashing. First, just for a moment, then solid. They stay on. I'm, curious, assuming the car may have charged to a point that the lights came on via "auto" lighting. I go outside and hear that familiar dinging sound going on and off. I go into the car, and the instrument cluster is freaking out. The car essentially thinks its being turned on and off rapidly, with the needles dropping down to 0, then all the dash lights come on, then the needles go back up, then repeat. It's not just the instrument cluster, however. The car itself starts RAISING and LOWERING on its own completely. Putting itself into ABC Sport Mode, and basically bouncing.

I immediately turned the car off. That **** freaked me out. After a few minutes, I mustered up the courage to go back and try to let it idle for a while longer. Perhaps, I think, maybe its reestablishing a charge and the electrical consumers and all trying to go back online.

That's where I sit now. It's still out my window, slowly getting closer to running out of gas on idle. I'm going to go out here when I'm done writing this post and turn it off.

Looks like I'm calling the dealership in the morning. Either way, with the car stuck in park and all this electrical nonsense, I don't think I'm equipped to understand the issues here. Any ideas? Wish me luck, boys. My car is possessed.

 

I experienced a lot of those symptoms when my Consumer Battery was going bad. Try having that tested.

 

No, not possessed, just water in the CAN network, possibly, did you have more rain than usual? Did you wash the car with a power washer? Could also be a bad EIS (ignition switch). Your symptoms suggest one of these options.
A Mercedes dealership will quote you more than the value of the car to fix it, I would guess.

 

Before I would take the car to a Benz dealership I would drop bricks on my foot. I trust them less than I trust my Ex wife!! The best place I know to take that car, if you decide you need to take it to someone who would figure its issues out, would be Auburn Foreign and Domestic. If you have Triple A, they could tow it there for free... They have four or five older former Mercedes dealership techs onsite and those guys know the cars well, and they always charge less money than a dealership is going to charge. Also they warranty everything they do, for longer periods of time than a dealership will! I have taken a few of my Benzos there and they are a family owned business for over 30 years with their reputation to care about. Greg there is great. If you do bring the car there, please tell him I sent you!
That said, I'm thinking if it is sitting out in the rain maybe water has gotten in somehow, to a CAN BUS or something like that. The best thing you can do for an R230 is drive it twice a week! Even if for only ten miles. I'm lucky, both my R230s and my Maserati stay in a dry garage and only come out on dry days. Neither of them have gotten wet in over three years! So if there was a water leak, I'd never know it.

 

Sorry tonylinc, I must disagree with you. The best thing you can for for an R230 is drive it every day. Double bonus, it's good for the driver too.

 

Yes, drive as often as possible! I was driving mine every ten days or so and that wasn't enough, so I switched to once a week.
Then, as weather permits, twice a week. Spring and summer are on their way here, so it will be more like every day or two.
With six cars it can be hard to drive each of them every day. LoL I was thinking of selling one, but then.... I couldn't decided which one.
There's a 2004 SL600 with under 50K miles on bringatrailer dot com! I Must stay away from the computer!!! LOL

 

Absolutely right. Look into the air inlet of the vent system. If there is visible water, the drain is blocked, and you have water in the passenger side, underneath the carpet. There is a Canbus C connector underneath the carpet, right side, and if that gets water, it either short circuit or create connection to ground.

The car then behaves exactly as you describe.

 

Have you tried to start the car with a battery you know is in good working order before starting to take anything apart?

Also if the car is always standing outside why not buy a cheap outdoor cover? Then you will eliminate the chance for water getting into your car

 

Definitely look at where SLcharge said to look, looking in there is a must, if the drain by the hood vent is plugged with pine needles or tree debris you must address that!!

 

I'm having similar problems with my 2012 SL63 AMG which has been sitting for 5-8 months thanks to this covid *****. Yesterday being a beautiful day I decided to start it up and check things out. As soon as I put the key into the switch the washer started pumping spraying fluid all over. The engine started OK but the washer kept pumping until it was empty and still kept pumping. Some troubleshooting showed the battery in the trunk was dead. I replaced it today and am still having all kind of problems, mainly the washer pump running along with lights being on, windows not working properly etc. Any ideas? I pulled the fuse in the engine compartment (f14 7.5 amp) and it kept running. I must note that inside the fuse box was wet which I dried the best I could and blew it out with air. Is there anything else on that side of the car that could be what I'm hearing, under the battery?