2001 Yamaha YFM660 Raptor Factory Service Manual, Page 320Get this manual
COOLING SYSTEM
6.Thermo switch 1
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