What was found
APPROX. 3 MINUTES AFTER SELECTING ENGINE INTAKE HEAT ON, THE LEFT INTAKE LIGHT ILLUMINATED, COMPLETED QRH. 2 SECONDS AFTER RESELECTING LEFT INTAKE LIGHT ILLUMINATED AGAIN. NO CB'S WERE POPPED WITH LEFT ENGINE ANTI-ICE ON ALL ENGINE INDICATIONS INDICATED THAT THE SYSTEM WAS OPERATING NORMALLY. LEFT INTAKE LIGHT REMAINED ON CONTINOUSLY WITH LEFT ENGINE ANTI-ICE SWITCHED IN THE ON POSITION. MAINTENANCE CLEANED CANNON PLUGS ON SHOEBOW AND SWAPPED THERMISTERS. RAN AIRCRAFT PER SF340 MM CHAP 30, ALL CHECKS GOOD AT THIS TIME.