2008 Polaris ATV Sportsman 300 400 H.O. Service Manual, Page 215Get this manual
ELECTRICAL Troubleshooting
Starter Motor Does Not Run Battery dischargedLow specific gravity Loose or faulty battery cables or corroded connections (see Voltage Drop Tests) Related wiring loose, disconnected, or corroded Poor ground connections at battery cable, starter motor or starter solenoid (see Voltage Drop Tests) Faulty key switch or OffRun Switch Faulty transmission switch Faulty Start Diode(s)Use digital multi-meter to test diode operationLocate the diode(s) in the main harness under the hi-temp conduit and measure between the diode connectionsContinuity should flow one direction only
Voltage Drop Testing
The Voltage Drop Test is used to test for bad connectionsWhen performing the test, you are testing the amount of voltage drop through the connectionA poor or corroded connection will appear as high voltage readingVoltage shown on the meter when testing connections should not exceed 0.1 VDC per connection or componentTo perform the test, place the meter on DC volts and place the meter leads across the connection to be testedRefer to the chart on 9.35 to perform voltage drop tests on the starter system