1992 300SD OM603.971

I'm trying to figure out if my instrument cluster engine temperature gauge is correct.

The ECT gauge sensor (B13) is installed in a bunghole in the head and the EDS (control) sensor (B11/4) is installed just downstream of the thermostat in its head.

I have the specs for the ECT gauge sensor and the EDS (control) sensor. Can you compare the temperature from those two sensors - given their different locations? Can I expect those two temperatures to be the same?

I got the engine up to ~90c (instrument cluster gauge), turned off the car, unplugged the EDS sensor and measured its resistance - its temperature was considerably less (15-20 degrees) than the instrument cluster gauge indication.

I may have the opportunity to make some better measurements using an IR pyrometer, thermocouple in the thermostat discharge hose, and/or a contact thermocouple. If I can find the connector and rustle up some resistors, I should be able to check the instrument cluster gauge.

thnx