I have a question about the coolant temp sensors on my 81 300D. I noticed that there are two of them, one above the thermostat and another between the 2 & 3 cylinders glow plugs. Which one is for the gauge on the dash?

I noticed on the wiring diagram for the glow plug system that there is a temperature sensor for the glow plug system. Could the one between the glow plugs be for that purpose?

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1981 Mercedes 300D