QRH Procedure still valid on our oldest A321 Lady:
TOO HOT/COLD COCKPIT AND CABIN TEMPERATURE IN FLIGHT
Apply the procedure if the cockpit and cabin temperature become too hot or too cold with the temperature selector at its maximum cold or hot selection :
PACKS OUTLET TEMP (ON ECAM BLEED PAGE).......................................CHECK
If difference between both packs is below 10 °C:
AIR COND HOT AIR switch...................................................... .......................OFF
A difference between both packs lower than 10 °C may reflect a mixer temperature sensor failure. Switching OFF the HOT AIR results in the use of the duct temperature sensors only and no longer in the use of the mixer temperature sensors. A normal cabin and cockpit temperature will be recovered.
If difference between both packs is at or above 10 °C:
PACK (WITH THE HIGHEST OUTLET TEMP)............................................... OFF
A difference between both packs of 10 °C or greater than 10 °C may reflect a contamination of packs resulting in too hot cabin and cockpit air temperature. The situation may be alleviated by switching OFF the pack discharging the hottest air.