Ok. Alot of the W126 had the old style alum fuses. They make an upgrade kit via ************** that uses copper replacements. Try spraying the fuses with wd-40 and rolling each one with your finger prior to starting it of course. If your radio is not working along with your pwr windows, this could be your culprit. I think the windows and radio are on the same fuse; ck your owners manual. Your connection on the batt may be in question; Try cleaning you terminals. The acc woes may also be secondary to terminals within the unit where it plugs into the wire harness behind; Use the search and you will find that many, like myself, had sucess resoldering the terminals. Fixed all my acc problems. Easier than spending 300$ for a new unit. The neutral safety sw: Verify a good batt, hold the key to sart with your left hand and work the shifter up/down. Your nss may just have a little corrosion. Had this happen to mine. The PO of my had it sitting outside for two years before I got it. Had all these issues and more. Finally, when you get it started, drive it..hard! You can't hurt it. The heat and vibrations may alleviate some other issues. Good luck