What was found
AFTER EXTENDING LANDING GEAR MAIN LIGHTS ILLUMINATED ONLY. UNLOCK LIGHT WAS NOT ILLUMINATED, CYCLED GEAR WITH SAME SITUATION . DID FLY BY WITH TOWER WHO INDICATED NOSE GEAR APPEARED TO BE DOWN AND LOCKED. DURING CLIMB TO PATTERN ALTITUDE NOSE GEAR LIGHT ILLUMINATED. INSPECTED NOSE GEAR DOWN LOCK SWITCH, CONNECTOR PLUG. FOUND TO BE CORRODED. REMOVED CONNECTOR PLUG AND CLEANED / REMOVED CORROSION. REINSTALLED CONNECTOR PLUG. JACKED A/C AND PERFORMED GEAR SWING. GEAR SWING CHECKS GOOD. NO FURTHER DEFECTS NOTED AT THIS TIME. WORK DONE IAW AMM 20-20-01.