So i picked up a 02 s430 about a month ago , i needed the 4 doors. I enjoy the car , its a pleasure to drive , however after the first week after sitting overnight my car would require a jump start due to a very weak battery. So i know these 2 brothers who own a high end auto repair shop , they work on my other car all the time. I believe they said the last battery had a dead cell in it. (looked like a old battery) came with the car. Anyway they had battery they had just come out of a s500 , the battery looked to be in -like new- condition. They threw it in the trunk. For a few weeks all was good , now the problem has returned. If my car sits for a period of longer than 4 hrs my battery will be dead. This leads me to think something is not turning off and is just draining the battery. Is there a common problem out there that i could check? or any idea's out there?

 

the radio head unit was a common draw issue. try to remove the fuse for the radio/COMAND unit and see if the battery draw stops.

 

^ thats the type of post i was looking for , i will def try the radio fuse. So me thinks its under the back seat , but do you happen to know which one im looking for? my car did not come with a owners manual.

 

either under the hood driver side (left) fuse box #22 15 amp or rear fuse box under the seat fuse #60 7.5 amp.


or rear fuse box #61 7.5 amp
possibly left front fuse box #23
depends on the production date of your car.

 

You can do a parachutic draw test with a volt/ohm meter. There are several videos on YouTube that demonstrate how to do it. If you don't want to do it yourself, your friends at their shop should be able to it in no more than hour including isolating the offending circuit.

 

Sorry... PARASITIC

 

^ Thanks for the idea , those friends at the shop seem to think its the aftermarket amp i installed. the stock amp was missing and i had no sound , so i purchased a small aftermarket amp to get sound , however it was not installed correctly.