2001 Yamaha YFM660 Raptor Factory Service Manual, Page 314Get this manual
SIGNAL SYSTEM
4.If the coolant temperature warning light does not come on when the start switch is pushed on, or if the coolant temperature warning light does not come on when the temperature is high (more than 117123 (242.6253.4 F)): 1.Bulb and bulb socket
NO CONTINUITY
Check the bulb and bulb socket for continuityCONTINUITY Replace the bulb andor bulb socket
2.Thermo switch 2