Temp gauge quit working on me last week, (fuel & oil pressure still work).

1. Using a 9V battery quickly across the temp gauge terminals causes the gauge to work.
2. Jumping the temp sender wire to ground does not cause a reading on the gauge.
3. The temp sender reads about 200 ohms to battery negative (engine not hot).
4. The temp gauge 5V lead shows conductive path to the pin on the dash harness (no crack in the circuit board).

I don't read pulsed 5V anywhere.....more like maybe 1, but its tough to read.
If my IVR is on the way out, will the temp gauge be the first to stop working?
How would you proceed?