What was found
ON FLIGHT 3006, CREW REPORTED AIR/GND FAIL MESSAGE WHEN RETRACTING THE LANDING GEAR. GEAR REMAINED DOWN WITH 3 GREEN LIGHTS. AIRCRAFT REMOVED FROM SERVICE. REMOVED AND REPLACED NOSE LANDING GEAR HARNESS IAW EMB140 AMM 32-61-02. PERFORMED OPERATIONAL CHECK ON LANDING G EXTENSION AND RETRACTION IAW EMB 140 AMM 32-30-00. OPERATION CHECK GOOD. FOUND PIN BROKEN ON NOSE NLG PROX SWITCH AND REMOVED AND REPLACED NOSE LANDING GEAR PROX SWITCH IAW EMB 140 AMM 32-68-02. AIRCRAFT RETURNED TO SERVICE.