Coolant level is a chassis (cooling system) function rather than engine or coach brand. Is your Dutch Star on a Spartan or Freightliner chassis?
I'm not familiar with your particular rig, but typically the sensor is just a switch, so is either open or closed and can be tested with an ohmeter. The sender wiring can be tested by disconnecting from the sensor (should be open) and shorting the wires together to simulate a closed sensor switch.