If you're talking about the 85, I'm pretty sure the temperature sensor for the glow plugs is in the relay itself. Earlier models had it in the head. Don't know if this means the sensor is for the EGR computer or not. There's also a climate control low coolant temperature cut out sensor somewhere. That sensor is on the servo in early models. Perhaps MB just converted a glow plug temp sensor to climate control sensor on later models without the servo.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13