What was found
(CAN) PILOT REPORTED GEAR WOULD NOT LOCK WHEN SELECTED DOWN THE EMERGENCY HAND PUMP WAS USED TO LOCK GEAR AND INDICTION WORKED AND LANDING WAS UNEVENTFUL.MAINTENANCE AT THE BASE DID GEAR FUNCTIONAL TEST AND IT FUNCTIONED NORMAL, THE PRESSURE SWITCH CANNON PLUG WAS CLEANED.WHEN AIRCRAFT RETURNED TO BASE THE SYSTEM WAS FUNCTIONAL TESTED AGAIN AND WATER STAINS WERE OBSERVED IN THE HYDRAULIC AREA.ALL ELECTRICAL CONNECTORS WERE CLEANED AND TREATED WITH PRODUCT RECOMMENDED BY AIRCRAFT MANUFACTURE. THE PRESSURE SWITCH WAS REMOVED AND CLEANED AND FUNCTIONAL TESTED WITH NITROGEN.