What was found
PUT LANDING GEAR HANDLE DOWN ON FINAL, 3 GEAR UNSAFE LIGHT ILLUMINATED AND NOTHING ELSE. GEAR DID NOT COME DOWN. 3 TO 4 MINUTES LATER GEAR CAME DOWN AND LOCKED AS NORMAL. TAPPED DOWNWARD ON GEAR HANDLE SEVEAL TIMES TO NO AVAIL. INTERROGATED PSEU AND CDS FOR FAULTS, NO FAULTS LOGGED. PERFORMED GVI OF ALL 3 LANDING GEAR. FERRIED ACFT TO PDX FOR REPAIRS. FOUND EXTENSION SELONOID ON LANDING GEAR CONTROL VALVE ELECTRICAL TEST OUT OF LIMITS IAW AMM 32-31-06-760-801. REPLACED LANDING GEAR SELECTOR VALVE IAW AMM 32-31-06-000-801 +32-31-06-400-801 TESTS GOOD. RETURNED TO SERVICE.