A Lead Mechanic reports an A320 aircraft arrived with an aft galley chiller deferred. Mechanics found an airflow duct not installed; lying in water and on electrical wires.

Narrative

An A320 aircraft had a deferred aft galley chiller inoperative. Two Aviation Maintenance Technicians (AMT) were assigned to deferred [chiller]. They performed an operational test per maintenance manual (MM) 25-34-51 and found no air flow at [connecting] ducts. They removed the chiller and discovered that the duct; item #150; reference Illustrated Parts Catalog (IPC) Chapter 25-33-03a was not installed; thus preventing airflow to duct. They were able to access the back of the galley through the trash compartment access panel in the aft lavatory. This is where they found the duct; lying on water and electrical lines. The aircraft had overnighted [this month] and an AMT had replaced the chiller; but in his defense an air flow check is not required per the maintenance manual; only an electrical check. But the aircraft just came from a #3 heavy check in December; [where] the galley was removed and replaced per MM 25-33-41 and does require an airflow check of chiller system. We installed the duct assembly and performed an operational check.