2004 Official factory service manual for Yamaha YFZ450S ATV Quad., Page 338Get this manual
SIGNAL SYSTEM 2Thermo switch Remove the thermo switch from the radiator Connect the pocket tester1) to the thermo switch as shown Immerse the thermo switch in container filled with coolant Place thermometer in the coolant Slowly heat the coolant, then let it cool down to the specified temperature Check the thermo switch for continuity at the temperatures indicated belowTest step 3 4 Coolant temperature Continuity Thermo switch Less than 120 (248 5.4 F) More than 120 (248 5.4 F) More than 115 (239 5.4 F) Less than 115 (239 5.4 F) NO YES YESELEC