A319 First Officer reported a pneumatic hot air valve malfunction during cruise; causing excessive temperatures in the cockpit and cabin. The crew continued to destination and landed; where maintenance determined the valve was deferred in the incorrect position.

Narrative

While at cruise (F310); we experienced very high flight deck air temperatures.After an almost three hour delay; caused by multiple Maintenance issues discovered on the preflight walk around on the gate at ZZZ; we received a HOT AIR FUALT ECAM. There were several occurrences of this issue previously documented. An ELB entry was made and hub Maintenance was contacted via frequency XXX.XX. Maintenance deferred the hot air valve; which involves closing the hot air valve manually (Maintenance function). The Captain and Maintenance verified the valve closed before departure. The aircraft was released once the MEL applied. The flight continued normally until halfway to ZZZ1 in cruise. Both cabin temp and flight deck temp were extremely hard to control. The cabin was cool while the flight deck was extremely warm. The Captain contacted Dispatch. Maintenance was contacted via ACARS as well and the Captain gave me the aircraft and radios. Troubleshooting continued with no luck. It was discovered that the hot air valve was in fact open (even though it should have been closed). The decision was made to continue on to ZZZ1. Flight deck temperature reached over 100 degrees at one point before landing. After landing; we thoroughly debriefed the event and informed the next crew of what we had experienced.