What was found
ZONE TEMP LIGHT CONT CAB ILLUMINATED ON RECALL. GROUNDED - YES. PERFORMED PZTC BITE ON CONT1/2 IAW B737-900 FIM 21-62 TASK 801. "FLT DECK - TRIM VALVE" RH CONT ON BIT, CLEARED (GREEN) ON VERIFY. CLEANED FLT DECK TEMP BULB IAW B737-900 AMM 21-61-10-100-801. PERFORMED OPS CHECK IAW AMM 21-61-00-700-807-002. LT NO LONGER PRESENT ON MASTER RECALL AT OVERHEAD. BOTH PACKS, ALL INDICATIONS NORMAL. RE-RAN BITE, NO FAULTS. TEMP BULB WAS VERY DIRTY, SUSPECTED AS CAUSE.