I am looking at a 1982 W123 wiring diagram and it shows a temp sensor inside the glow plug relay. I am wondering how that sensor operates and its exact function. Surely it is not the best place to measure engine temperature.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked