What was found
AFTER SELECTING ENGINE ANTI-ICE ON DURING DESCENT IN ICING CONDITIONS, THE RIGHT ENGINE TAI INDICATION WAS AMBER WITH THE RIGHT AMBER COWL VALVE OPEN LIGHT INDICATING DIM BLUE. AFTER A FEW MINUTES THE AMBER TAI INDICATION CHANGED TO GREEN. GROUNDED - YES. PERFORMED ENGINE COWL ANTI-ICE OPERATIONAL TEST PER B737-800 AMM 30-21-00-710-801. GROUND RAN #1 AND #2 ENGINES FOR 5 MINUTES, CYCLING #2 ENG ANTI ICE SWITCH NUMEROUS TIMES W/ NO DEFECTS NOTED. OBSERVED COWL VALVE OPEN LIGHT ON P5-11 PANEL ILLUMINATE BRIGHTLY THEN DIM EACH TIME. ALSO VERIFIED 'TAI' INDICATION ON MFD/ ED ILLUMINATED GREEN, NO AMBER, EACH TIME. NO PREVIOUS HISTORY 90 DAYS.