Battery drain on my 1980 300sd

[curbill]

On my 1980 300sd if you do not drive the car for 4 or 5 days you will not be able to start it. It has a brand new battery, new cables and 8I have replaced all fuses that were with aluminum ends with new brass ones. There are no open circuits. I have had the car at a shop and basically did the same thing in tracing any leakage. After sitting for 5 days nothing will allow the car to start without recharging the battery. The battery has been double checked and has less than 10 hours of use. My wife will not drive it and she just takes my 126 and leaves the 116 to me. As I do not go out every day I have installed a shutoff on the neg. cable side. Really at a loss as to what is causing it. While the engine is running the alt. is charging????? Thank you

[Hirnbeiss]

The only correct answer is that something is causing a drain. Pull fuses to isolate which one.
The fact that your negative shutoff switch works proves it.