My drivers side headlight wiper motor stopped working, so I bought a used one. Installed it this eve, it works, but not like it should. When you pull the washer handle and hold it on to activate the headlight wipers, both move as they should, but when I let go of the washer handle, the drivers side usually stops in the up position while the passenger side continues to wipe for another second or two before it settles down where it should. If I tap the washer handle on and off for a split second, the drivers side moves only step by step with me so I can get it down where it belongs, yet as I tap the washer handle for split seconds, the passenger side will wipe in full motion as it should. Why does this happen? Is this used motor bad? Is there any adjustment that can be made to the motor so it cycles full to the stop position?