2001 Polaris Sportsman 400-500 DUSE and H.O. Service Manual, Page 367Get this manual
ELECTRICAL
COOLANT TEMPERATURE SENSOR TEST (HOT LIGHT)
With the ignition switch (and engine stop switch) "ON", power is delivered to the hot light via the RedWhite wireThe BlueWhite wire (ground) out of the light socket is connected to the coolant temperature sensor on the cylinder headIn normal operating conditions, the temperature sensor is non-conductive (open)If engine coolant reaches the specified temperature, the sensor becomes conductive completing the ground path for the lightWith engine cold, disconnect lead and measure resistance of sensor between connector terminal and groundThere should be no continuity or very high resistance (megohms)To test the "ON" temperature, heat the switch in water bath to the temperature shown in table belowThe switch should become conductive (low resistance) at indicated temperatureDo not immerse switch past the threads or allow switch to contact container when heatingHot Light On 221 (105 C)