2002 Yamaha YFM660 Grizzly factory service and repair manual, Page 394Get this manual
COOLING SYSTEM
6.Thermo switch 2
C0NTINUITY
Remove the thermo switch from the radiatorConnect the pocket tester10) to the thermo switch 1Immerse the thermo switch in coolant 2Check the thermo switch for continuityWhile heating the coolant use thermometer to record the temperaturesTest step