2004-2005 660 Yamaha Rhino Factory Service Manual, Page 400Get this manual
COOLING SYSTEM
6Thermo switch Remove the thermo switch from the radiator Connect the pocket tester1) to the thermo switch Immerse the thermo switch in coolant Check the thermo switch for continuityWhile heating the coolant use thermometer to record the temperatures The thermo switch circuit is closed The thermo switch circuit is open