2012 Sportsman 400/500 and EFI Tractor Service Manual 9923412, Page 278Get this manual
FINAL DRIVE Front Gearcase Diagnosis
Symptom: AWD Will Not Engage 1Check the gearcase coil resistanceTo test the gearcase coil resistance, use the coil harness (GreyBrownWhite)NOTE: To test the gearcase coil resistance, use the AWD coil harnessThe gearcase coil should measure between 22.8 ohms and 25.2 ohms3Inspect the armature plate for consistent wear patternThere should be two distinct wear bands (one band inside the other)If only one band of wear is present (or if there is wear between the two bands, inspect the coil area as indicated in Step 4A band with an interrupted wear mark may indicate warped plate, which may cause intermittent operation
Armature Plate
Check for Wear Bands
4Check to make sure the coil is seated in the Ushaped insert that is pressed into the gearcase coverThe top of the coil should be seated below the Ushaped insertThe U-shaped insert controls the pole gapIf the top of the coil is above the surface of the U-shaped insert it raises the armature plate, thereby increasing pole gapIf the pole gap increases the coil will not be strong enough to engage the AWD systemIf this is the cause order new Cover Plate AssemblyCutaway View of Gearcase Cover