What was found
LEFT BLEED AIR FAIL LIGHT ILLUMINATED DURING CLIMB OUT OF BFI. EMERGENCY PROCEDURE CHECK FOR THIS CLEARED, THEN WARNING LIGHT RETURNED. LEFT BLEED AIR VALVE WAS PLACED IN THE PNEUMATIC AND OFF POSITION. LIGHT THEN CONTINUED AT FLIGHT LEVEL 300. APPROXIMATELY 30 MINUTES AFTER TAKE OFF, THE LEFT BLEED AIR LIGHT FAIL LIGHT WAS ILLUMINATED AGAIN WITH THE BLEED AIR VALVE SWITCH IN THE NEUTRAL POSITION. THE CREW REVIEWED THE EP AGAIN AND RETURNED TO BFI. PILOT IN COMMAND DECLARED AN EMERGENCY WITH ATC. LEFT BLEED AIR LIGHT EXTINGUISHED WITH POWER REDUCTION DURING DECENT.