What was found
(CAN) ON APPROACH THE LANDING GEAR WAS SELECTED DOWN ALL THREE GEAR STAYED UP AND LOCKED. AN EMERGENCY GEAR EXTENSION WAS COMPLETED AND THE AIRCRAFT LANDED WITHOUT FURTHER INCIDENT. MAINTENANCE JACKED THE AIRCRAFT AND ATTEMPTED TO COMPLETE GEAR SWINGS WHEN THEY SELECTED GEAR UP THERE WAS NO RESPONSE. MAINTENANCE FOUND THAT THE LANDING GEAR SELECTOR VALVE SOLENOID DID NOT MAKE ANY NOISE WHEN THE GEAR SELECTOR WAS UP OR DOWN. THE LANDING GEAR SELECTOR VALVE SOLENOID WAS REPLACED AND THE GEAR SWUNG WITHOUT FURTHER INCIDENT.