What was found
CREW REPORTED, LANDING GEAR AIR/GROUND FAIL MESSAGE APPEARED AFTER TAKEOFF, MESSAGE WENT AWAY AFTER 5 SECONDS. MAINTENANCE FOUND NOSE LANDING GEAR STRUT OVERSERVICED, SERVICED STRUT TO PROPER LEVEL; AND CLEANED RIGHTHAND MAIN LANDING GEAR FORWARD WEIGHT ON WHEELS SWITCH CONNECTOR. OPS CHECKED SYSTEM GOOD. AIRCRAFT RETURNED TO SERVICE.