Down on the bottom board there are 2 large square units in the center. These units have 2 coils, one coil steps the unit, the other resets it. When you manually push the lever that connects to one coil, you should see the unit move one step each push through 4 positions. When you push the lever on the other coil the unit should freely slide back to the first position. Your machine is not doing that. The probable reason for that is that the unit is dirty. The fix is easy and usually takes half an hour to complete. I've done it a hundred times. Disassemble the wiper arm from the axle and clean those arm contacts and the rivets on the unit with metal polish. Put it back together and manually test it. If the unit resets freely you should be back in business. If it does not, check to see if one of the several springs on the mechanism is broken or missing. Also check the lever mechanism and ratchet disc for excess dirt or grease and clean. A clean unit is a happy unit. If it looks good but still doesn't reset freely, you will need to increase the tension on the large round spring on the axle by moving it a to the next available hole on the ratchet disc. Hope this helps.