2005 Polaris Sportsman 400/500 Service Manual, Page 274Get this manual
ELECTRICAL
SPEEDOMETER TROUBLESHOOTING CONT'D
TEST- RESET SPEEDOMETER -If the key switch or engine stop switch is turned off with the vehicle in motion, the speedometer indicator needle may stick, indicating the speed at which the vehicle was traveling when the speedometer lost powerFor example: If the ATV was traveling 30 mph when the engine stop switch is turned off, speedo may indicate 30 mph until reset: 1Operate vehicle at speed greater than indicated on speedometer (past point where needle is stuck)Needle should return to normal operation2In the above example, the ATV speed would have to exceed 30 mph to reset
COOLANT TEMPERATURE SENSOR (THERMISTOR) TEST
FAN MOTOR CURRENT DRAW
A current draw test will provide good indication of fan motor conditionA worn or damaged fan motor will draw more current, which causes reduction in blade speed and reduced coolingFan Motor OrBlk OrBlk Brn Connect ammeter to OrBlk in series If the thermistor circuit is open the engine Hot light and fan will both come onWith engine cold, disconnect lead and measure resistance of sensor between the two YellowBlack connector terminalsThere should be no continuity or very high resistance (see chart below)See "Engine Temperature Controller" on Page 10.5 for information on thermistor operationSITUATION Hot light ONFan ON Hot light ON OHMS READING Above 50k DIAGNOSISACTION Open ThermistorReplace Thermistor Engine Overheat or Bad Thermistor