Aloha Nui ~
I am new to this forum..and not too car engine savvy. I inherited my stepdads 2001 S 500 when he passed away. Found out it's S430, no clue why there is a 500 on trunk. Then someone told me its to detract the thieves from stealing this model (500) bc no one wants to deal with a stolen 500!! Brilliant. Funny. It was bought brand new in Newport Beach at Fletcher Jones Motors in 2001. He barely drove it anywhere and I drove it around for errands just to keep the battery charged. So low miles for its age. It's a dream on the 5 to Socal though..like driving a sofa / king size bed down the freeway and easily gets up to 100mph without realizing it. I plan to drive it back to Rancho Mirage in month if I can get it repaired and somewhat reliable.

I drove it around a bit before it sat bc I have my own vehicles. Its now sat for 2 yrs since "a mobile mechanic" dropped by to "fix" it, by replacing the battery and leak in front tire. This was in 2021. He removed the tire and rim put in on a block removed the battery and never returned. He never sent us an invoice either. I recently located and got the rim and tire back, just ordered another battery, and am about to order new set of tires and reconditioned rims. It's in really good cosmetic condition ext/int. low miles..around 65,000?

No real cosmetic damages ext/int. Needs a good wash and detail. Has some moss growing out of the trim. I may sell once I can get it running, but right now I'd just like it to be operable. I loved driving it when it ran...SO smooth. Handles amazing on hills and wet weather. Freeways are easy. It does have that stupid navigation system with cd changer installed and I think someone may have disconnected it bc of the drain. Also has a phone hard wired into it.

Here was our issue with it in 2020 during pandemic; once we put a new battery in, would drain the new installed battery within a week or two. We had no one to work on it (bc we live on an island off WA state) and no one who had any real engine skills, could figure out the problem of electrical drain. We tried to check all the fuses and all the lights seemed to be off. I read on this forum about the door being left on if the lever isn't perfectly down, and had no idea there were so many sensors that could drain it if they were slightly left on or ajar.. etc. The glove compartment is stuck and cannot open so no idea if there is a bulb stuck left on. Brake lights used to stick without my lifting with foot. Other than this..no idea where to begin. A local auto garage said they are willing to put tires on but not sure if they are able or willing to check on the electrical bc they refuse to work on Porsche and other German cars. I have a Cayenne so Im often installing the battery myself and other work. My question is: Where should I begin to look once I get the battery installed in trunk again (weighs so much OMG..and its in a terrible location hard to install, back breaker) bc Im afraid I'll hook it up and then it will drain again. I wish I had a bypass way to keep it plugged into a wall charger (battery charger) with a relay switch ? Any ideas are appreciated sorry I can't give more info and I'm also not savvy on acronyms so if you do leave me a reply could you please write out the whole word (and I can google it) ... thank you so much !!! Mahalo~ Julie

 

Even with no excessive drain these cars will kill their battery after 2-3 weeks of non use . You can’t keep one of these cars stored and expecting to start up unless you install a remote control battery disconnect . See pic from Amazon attached . Just click the remote And the battery is disconnected and can’t drain

I put these on all my rarely used cars and it solves the issue

 

Another way is use a "battery maintainer", which is a small intelligent charger that can stay hooked up. Most have a connector in the cable going to the battery, so you can attach that short cable semipermanently to the battery, and hang the connector just outside the trunk lid. Plug in while parked, unplug and drive away, reattach when you get home. Just put some kind of warning on the driver's door or the steering wheel to remind you to disconnect.

If you haven't discovered this yet - There are numerous things that might need to be reset after a battery dies. For example, if you sunroof doesn't behave well, press the button to open it, then hold the button for ten seconds after it is full opened. Repeat for closing. If necessary, repeat for each window, for the steering wheel adjustment, headrest adjustment, etc., etc.Another major reset is to have the engine running, car still, turn the steering wheel all the way light, all the way left, all the way right and back to center,

 

I favor keeping the battery maintained rather than disconnected. Regarding the battery drain, you need to do a thorough inspection of ALL the cables and wiring. Cars that get parked even for a couple days can become habitats for rodents that will chew up stuff. They'll eat up the wire insulation, exposing bare conductors that can short out to one another. I assume you've already put a current clamp on the main battery cable and have pulled fuses one by one(?).