What was found
RT BLEED LIGHT ACTIVATED, CREW RAN AFM CHECKLIST AND DECIDED TO RETURN FOR LANDING. WHILE RETURNING FOR LANDING SOME LIGHT SMOKE WAS BEING EMITTED BY AFT DIVAN. ACFT LANDED WITHOUT INCIDENT. MECHANIC TROUBLESHOT SYS AND DETERMINED THAT THE WING HEAT VALVE FAILED IN THE FULL ON POSITION, WHICH ALLOWED UNREGULATED RAW BLEED AIR FROM ENGINE BLEED AIR MANIFOLD TO THE WINGS. THIS CAUSED SOME SINGING OF THE CARPET AT THE AFT DIVAN WHERE THE DUCTING ENTERS THE CABIN. WING HEAT VALVE WAS REPLACED WITH AN O/H VALVE & FUNCTIONALLY CHECKED. CARPET IS SCHEDULED TO BE REPLACED IN AFT DIVAN AREA.