Every connection is a suspect. Since it makes a connection at the light switch first before going to the starter solenoid, it wouldn't hurt to check /clean/ tighten that connection, as well as other connections such as battery terminals etc.

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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