Water temp gauge

[canyonero]

All apologies if this has been covered, I couldn't find an answer in the archives..
I can't tell if the water temp gauge on my SIII is working, or if the engine is really just staying VERY cool. I drove around running errands for about an hour today with the radiator muff fully buttoned, stop and go driving, probably 15-20 miles, 30-35 degrees. No movement from the water temp needle, the oil temp moved a little, and when I was finished, I could hold my hand on the radiator, both top and bottom. I don't drive it very far or fast often, and other than an occasional "Dieseling" after I shut it off, it runs pretty smooth; so I'm just curious if it's my gauge, thermostat, any thoughts?
Thanks

[SafeAirOne]

Do you have an electrical water temp sender or a mechanical setup on your ex-MoD?

Did the needle stay in the bottom of the white "cold" arc the whole time? If so, that doesn't sound right, even if you have no thermostat installed.

Temps were the same here today and my colder-running diesel moved off the white arc within 2 or 3 minutes of driving.

If you have an electrical sender, you can unplug the sender and substitute a 75-90 ohm resistor (one end on the wire, the other end grounded) and check that the needle is somewhere in the middle/upper middle range on the gauge (190-180 degrees).