2003 Yamaha YFM400FAR Kodiak Factory Service Manual, Page 346Get this manual
SIGNAL SYSTEM
4.If the coolant temperature warning light does not come on: Check that the light comes on when the main switch is set to "ON"G Check that the light comes on when the coolant temperature is 120 (248 5.4 F) or higher and that the light remains on when the coolant temperature drops to 113 (235.4 F)NO CONTINUITY
1.Bulb and bulb socket Check the bulb and bulb socket for continuityCONTINUITY 2.Thermo switch (cylinder head)
Replace the bulb andor bulb socket