I just did this mod on my 85 300D. When you get into a hot car, the first thing you want to do is open the windows. This mod will allow you to do that without having to put the key in the ignition first. If you already shut the engine off and forgot to close the windows, you can close them without fumbling for your keys. I have had this mod in my 83 300D for 3 years now without any problems. YMMV.

Disclaimer: Use this at your own risk. If you have kids, this mod is probably not a good idea.

1. Disconnect battery - terminal.

2. Remove the upper right (fuse c aux fan) and upper left fuse (fuse a power window )

3. Strip a short length of 12 gauge wire and shove the ends in the upper fuse clip holes of fuse c and fuse a as shown.

4. Put fuses back, which will secure and make contacts with the wire. Check that you have made a good connection by tugging on the wire lightly and make sure that it won't come out.

5. Connect battery - terminal and you're done.

Enjoy!

How it works:
Power is taken from the aux fan fuse c upper contact (hot at all times) to supply power to the window switch fuses a and b, bypassing the window relay (which is normally energized by the ignition switch in the start or run position). This mod is quick! (takes me less than 2 minutes).

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked