Temp Gauge & Sensor Specs?

[2ndwind]

"82 FI

My temp gauge died overnight.
All was fine, fan came on (and still does) at abt. 195 degrees, etc.
New sensor about 4 mos ago (<200mi)
gauge blips up just a bit when ignition turned on
After running the car for 45min., no change.
resistance at sending unit 345 ohms after about 20 minute warmup
12 volts at gauge and at plug for sending unit.

Brad Artigue's wiring diagram shows the "resistor" I've read about on this forum, is for an idiot light only. it is not directly in the circuit between the temp gauge and sensor.

I have no access to another gauge. My electronic friend would like to put a variable resistor in-line to test the gauge. Does anyone know the resistance range of the gauge?

Thanks